Nmap Public Source License Version 0.95 - Annotated HTML Description

The NPSL itself is rather terse, so we have created this Annotated HTML Nmap Public Source License in a best-effort attempt to make it easier to understand. This version includes further explanations and reasoning behind the license terms. These annotations are not part of the license itself, a legal document, or legal advice. If you need to know exactly what the license requires, you need to read and understand the license itself; if you need legal advice, talk to a lawyer.

The annotations (such as the one you are reading now) should be rendered as gray boxes to distinguish them from actual license text. You can also read a pure text version of this license without annotations.

This license is based on the GNU General Public License, version 2 (Exhibit A). Certain terms and conditions in this license come from the Apache License, version 2.0, the RealNetworks Public Source License, and the Academic Free License, version 3.0.

0. Preamble

The intent of this license is to establish freedom to share and change the software regulated by this license under the open source model. It also includes a Contributor Agreement and disclaims any warranty on Covered Software. Companies wishing to use or incorporate Covered Software within their own products may find that our Nmap OEM product ( better suits their needs. Open source developers who wish to incorporate parts of Covered Software into free software with conflicting licenses may write Licensor to request a waiver of terms.

If the Nmap Project (directly or through one of its commercial licensing customers) has granted you additional rights to Nmap or Nmap OEM, those additional rights take precedence where they conflict with the terms of this license agreement.

Open source authors: If your license is not compatible with this one, we are sometimes willing to grant permission to use portions of Nmap under a different license than this one (such as plain GPL or BSD). Contact Gordon “Fyodor” Lyon for permission.

Proprietary vendors: This license generally forbids selling proprietary software and hardware products that include and depend on Nmap for their functionality. This includes stand-alone software distribution or inclusion on a hardware appliance, docker container, virtual machine, etc. We do sell licenses which permit this as part of the Nmap OEM program which funds the Nmap Project. Hundreds of software vendors already license Nmap OEM to perform network discovery for their products. Other Nmap OEM benefits include commercial support, updates, and a custom Windows installer offering silent installation and an OEM version of our Npcap Windows packet capturing library. Prices and more details are available here.

This License represents the complete agreement concerning subject matter hereof. It contains the license terms themselves, but not the reasoning behind them or detailed explanations. For further information about this License, see . That page makes a good faith attempt to explain this License, but it does not and can not modify its governing terms in any way.

1. Definitions

2. General Terms

Covered Software is licensed to you under the terms of the GPL (Exhibit A), with all the exceptions, clarifications, and additions noted in this Main License Body. Where the terms in this Main License Body conflict in any way with the GPL, the Main License Body terms shall take precedence. These additional terms mean that You may not distribute Covered Software or Derivative Works under plain GPL terms without special permission from Licensor.

You are not required to accept this License. However, nothing else grants You permission to use, copy, modify or distribute the software or its derivative works. These actions are prohibited by law if You do not accept this License. Therefore, by modifying, copying or distributing the software (or any work based on the software), You indicate your acceptance of this License to do so, and all its terms and conditions. In addition, you agree to the terms of this License by clicking the Accept button or downloading the software.

3. Derivative Works

This License (including the GPL portion) places important restrictions on derived works. Licensor interprets that term quite broadly. To avoid any misunderstandings, we consider software to constitute a "derivative work" of Covered Software for the purposes of this license if it does any of the following:

This list is not exclusive, but is meant to clarify Licensor's intentions with some common examples. Distribution of any works which meet these criteria (and that also choose to accept this license to benefit from the rights granted herein) must be under the terms of this license (including this Main License Body and GPL), with no additional conditions or restrictions. They must abide by all restrictions that the GPL places on derivative or collective works, including the requirements for distributing their source code and allowing royalty-free redistribution.

Licensor does not purport to control through this license any software which does not require the rights granted herein (such as rights to redistribute and/or incorporate Covered Software executables and source code). In particular, many software packages include the ability to parse Covered Software results provided by an end user or to execute Covered Software that end user may have already installed on their system. To the extent that copyright doctrines such as fair use allow their practices without the need to exercise any rights granted by this license, vendors and distributors of such software are not bound by our definition of derivative works or any other clauses in this license.

The idea here is to prevent companies from using open source Nmap in their proprietary software or appliances. Some have in the past distributed Nmap executables as part of expensive proprietary products and refused to make the source available, claiming a loophole based on strange interpretations of the GPL definition of derivative and collective works. If companies take value from Nmap, they need to contribute back to the project and the open source community by either making their product/project compatible open source or buying a commercial license.

Please note that this "derivative work" definition only applies to parties who choose to accept this license in return for the special rights granted (such as Nmap redistribution rights). There are many applications with features involving parsing Nmap output provided by the end user or even executing a copy of Nmap provided by the end user that are not bound by this license at all. Software which often falls into this (exempt) category depending on the specific circumstances includes:

  • Libraries for parsing Nmap results in a given language.
  • Software programs which provide the ability for users to import their own Nmap results for parsing.
  • XSL stylesheets for converting Nmap output to another format
  • Graphical Nmap frontends for providing an alternate interface for Nmap users
  • Shell scripts and other programs which may rely on a user's existing copy of Nmap to accomplish some of their functionality.

Parties who distribute the 3rd party software above along with Nmap generally must comply with this license to gain thoe Nmap redistribution rights. They would have to also comply with the 3rd party softare package licenses. General purpose Linux distributions which happen to offer both Nmap and 3rd party packages described above for users to choose from are covered by the "mere aggregation" clause of the GPLv2.

Another goal of this section is to help prevent companies and individuals from making and distributing malware-laden copies of Nmap. While criminal malware gangs are unlikely to pay attention to copyright law, we have also caught more mainstream companies such as CNET's doing this.

4. Contributor Agreement (Grant of Copyright and Patent Licenses)

Each Contributor hereby grants to Licensor a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare Derivative Works of, publicly display, publicly perform, sublicense, and distribute the Contribution and such Derivative Works in Source or Object form.

Each Contributor hereby grants to You and Licensor a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable (except as stated in this section) patent license to make, have made, use, offer to sell, sell, import, and otherwise transfer the Work, where such license applies only to those patent claims licensable by such Contributor that are necessarily infringed by their Contribution(s) alone or by combination of their Contribution(s) with the Work to which such Contribution(s) was submitted. If You institute patent litigation against any entity (including a cross-claim or counterclaim in a lawsuit) alleging that the Work or a Contribution incorporated within the Work constitutes direct or contributory patent infringement, then any patent licenses granted to You under this License for that Work shall terminate as of the date such litigation is filed.

Contributors may impose different terms on their Contributions by stating those terms in writing at the time the Contribution is made. Contributors may withhold all authority from Licensor to incorporate submissions by conspicuously marking or otherwise designating them in writing as "Not a Contribution" at the time they make the work available.

We absolutely encourage and appreciate code contributions! But we generally can't accept them with strings attached. It isn't fair to contribute code to Nmap, then sue the users because you claim that code violates a patent you hold. Similarly, we can't have people sending patches to the Nmap development list, then claiming copyright violation when we incorporate and redistribute them in Nmap. It is also important that we retain full rights to relicense new versions of Nmap, including incorporated Contributions. The inability to relicense code has caused devastating problems for other Free Software projects (such as KDE and NASM). We also make changes to this license from time to time. In addition, we sell commercial licenses under different terms, and we sometimes grant special licenses to other open source projects for license compatibility. Note that we cannot revoke or change the license for previously distributed versions of Nmap, so any changes we make would only apply to future versions.

In addition to granting rights to us and all Nmap users, you retain the rights as copyright holder to use your changes as you desire. If you don't want us to incorporate your changes into Nmap under these terms, just say so when you submit them (or don't submit them at all).

5. Disclaimer of Warranty and Limitation of Liability

Unless required by applicable law or agreed to in writing, Licensor provides the Covered Software (and each Contributor provides its Contributions) on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. You are solely responsible for determining the appropriateness of using or redistributing the Covered Software and assume any risks associated with Your exercise of permissions under this License.

In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall any Contributor be liable to You for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising as a result of this License or out of the use or inability to use the Covered Software (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if such Contributor has been advised of the possibility of such damages.

6. External Deployment

Some open source licenses require that any hosted solutions using the product must also be open source. We only ask that you give Nmap credit if you externally deploy it.

If You Externally Deploy Covered Software, such as hosting a website designed to execute Nmap scans for users, the system and its documentation must, if technically feasible, prominently display a notice stating that the system uses the Nmap Security Scanner to perform its tasks. If technically feasible, the notice must contain a hyperlink to or provide that URL in the text.

7. Trademarks

This License does not grant permission to use the trade names, trademarks, service marks, or product names of the Licensor, except as required for reasonable and customary use in describing the origin of the Covered Software.

The main goal here is to avoid confusion and ensure that users know what they are getting. If someone modifies and redistributes Nmap, they need to call it something else so that users know it isn't an “official” Nmap release. This clause also helps prevent folks from adding malware/spyware/adware and then redistributing it as Nmap. We have previously caught numerous organizations doing that, including CNET

While we don't want derivative works to be misrepresented as official Nmap releases, properly crediting Nmap is allowed and expected.

While this license doesn't grant permission to use the Nmap trademark, feel free to contact Gordon “Fyodor” Lyon for special permission if needed.

8. Termination for Patent Action

This License shall terminate automatically and You may no longer exercise any of the rights granted to You by this License as of the date You commence an action, including a cross-claim or counterclaim, against Licensor or any licensee alleging that the Covered Software infringes a patent. This termination provision shall not apply for an action alleging patent infringement by combinations of the Covered Software with other software or hardware.

9. Jurisdiction, Venue and Governing Law

This License is governed by the laws of the State of Washington and the intellectual property laws of the United States of America, excluding the jurisdiction's conflict-of-law provisions. Any litigation or other dispute resolution between You and Licensor relating to this License shall take place in the Northern District of California, and You and Licensor hereby consent to the personal jurisdiction of, and venue in, the state and federal courts within that District with respect to this License. The application of the United Nations Convention on Contracts for the International Sale of Goods is expressly excluded.

10. Npcap and the Official Nmap Windows Builds

The official Windows Nmap builds includes the Npcap driver and library ( for packet capture and transmission. That software is under its own separate license terms rather than this license. Therefore anyone wishing to use or redistribute both pieces of software must comply with both licenses. Since Npcap does not allow for redistribution without special permission, the official Nmap Windows builds that include Npcap may not be redistributed without special permission. Such permission can be requested by email to

11. Permission to link with OpenSSL

Licensor grants permission to link Covered Software with any version of the OpenSSL library from OpenSSL.Org, and distribute linked combinations including the two (assuming such distribution is otherwise allowed). You must obey this License in all respects for all code used other than OpenSSL.

12. Waiver; Construction

Failure by Licensor or any Contributor to enforce any provision of this License will not be deemed a waiver of future enforcement of that or any other provision. Any law or regulation which provides that the language of a contract shall be construed against the drafter will not apply to this License.

13. Enforceability

If any provision of this License is invalid or unenforceable under applicable law, it shall not affect the validity or enforceability of the remainder of the terms of this License, and without further action by the parties hereto, such provision shall be reformed to the minimum extent necessary to make such provision valid and enforceable.

Exhibit A. The GNU General Public License Version 2


Version 2, June 1991

Copyright (C) 1989, 1991 Free Software Foundation, Inc.  
51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.


The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Lesser General Public License instead.) You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.

To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.

Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations.

Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone's free use or not licensed at all.

The precise terms and conditions for copying, distribution and modification follow.


0. This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The "Program", below, refers to any such program or work, and a "work based on the Program" means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term "modification".) Each licensee is addressed as "you".

Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does.

1. You may copy and distribute verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the Program a copy of this License along with the Program.

You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.

2. You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions:

a) You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change.
b) You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.
c) If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License. (Exception: if the Program itself is interactive but does not normally print such an announcement, your work based on the Program is not required to print an announcement.)

These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Program.

In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.

3. You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following:

a) Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,
b) Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,
c) Accompany it with the information you received as to the offer to distribute corresponding source code. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.)

The source code for a work means the preferred form of the work for making modifications to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable. However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable.

If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code.

4. You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

5. You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Program or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Program (or any work based on the Program), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Program or works based on it.

6. Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients' exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties to this License.

7. If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Program at all. For example, if a patent license would not permit royalty-free redistribution of the Program by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program.

If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances.

It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.

This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.

8. If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License.

9. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation.

10. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally.





For brevity, we've cut out the GPL's final section on “How to Apply These Terms to Your New Programs”, but you can find it here.