Licenses

Table of Contents

Published software should befreesoftware. To make it free software, you need to release it undera free software license. We normally use theGNUGeneral Public License(GNU GPL), specifying version 3 or anylater version, but occasionally weuseother freesoftware licenses. We use only licenses that are compatible withthe GNU GPL for GNU software.

Documentation for free software should befree documentation, so thatpeople can redistribute it and improve it along with the softwareit describes. To make it free documentation, you need to releaseit under a free documentation license. We normally use theGNU Free Documentation License(GNUFDL), but occasionally we useother freedocumentation licenses.

If you've started a new project and you're not sure what license touse,“How tochoose a license for your own work”details ourrecommendations in an easy-to-follow guide. If you just want a quicklist reference, we have a page that namesourrecommendedcopyleft licenses.

We also have a page that discussesthe BSD License Problem.

Evaluating Licenses

If you come across a license not mentioned in ourlicense list, you can ask usto evaluate whether it is a free license. Please email a copy of thelicense (and the URL where you found it)tolicensing@fsf.org. Ourlicensing experts in the staff and the board of directors will reviewit. If the license has some unusual conditions, they may posedifficult philosophical problems, so we can't promise to decidequickly.

Common Resources for our Software Licenses

We have a number of resources to help people understand and use ourvarious licenses:

The GNU General Public License

The GNU General Public License is often called the GNU GPL for short;it is used by most GNU programs, and by more than half of all freesoftware packages. The latest version is version 3.

The GNU Lesser General Public License

The GNU Lesser General Public License is used by a few (not by any meansall) GNU libraries. The latest version is version 3.

The GNU Affero General Public License

The GNU Affero General Public License is based on the GNU GPL, but has anadditional term to allow users who interact with the licensed software overa network to receive the source for that program. We recommend that peopleconsider using the GNU AGPL for any software which will commonly be runover a network. The latest version is version 3.

The GNU Free Documentation License

The GNU Free Documentation License is a form of copyleft intendedfor use on a manual, textbook or other document to assure everyonethe effective freedom to copy and redistribute it, with or withoutmodifications, either commercially or non-commercially. The latest versionis 1.3.

Exceptions to GNU Licenses

Some GNU programs have additional permissions or special exceptionsto specific terms in one of the main licenses. Since some of thoseare commonly used or inspire a lot of questions on their own, we'vestarted collecting them onourexceptions page.

License URLs

When linking to our licenses, it's usually best to link to the latestversion; hence the standard URLs such ashttps://www.gnu.org/licenses/gpl.htmlhave no version number.Occasionally, however, you may want to link to a specific version of agiven license. In those situations, you can use the following links[skip links]:

GNU General Public License (GPL)
GPLv3,GPLv2,GPLv1
GNU Lesser General Public License (LGPL)
LGPLv3,LGPLv2.1
GNU Affero General Public License (AGPL)
GNUAGPLv3(TheAffero General Public License version 1is not a GNU license, but it wasdesigned to serve a purpose much like the GNU AGPL's.)
GNU Free Documentation License (FDL)
FDLv1.3,FDLv1.2,FDLv1.1

Stable links to each license's alternativeformats are available on its respective page. Not every version ofevery license is available in every format. If you need one that ismissing, pleaseemail us.

See also theold licenses page.

Unofficial Translations

Legally speaking, the original (English) version of the licenses iswhat specifies the actual distribution terms for GNU programs andothers that use them. But to help people better understand thelicenses, we give others permission to publish unofficial translationsinto other languages, provided that they follow our regulations forunofficial translations.

The FSF does not approve license translations as officially valid.The reason is that checking them would be difficult and expensive(needing the help of bilingual lawyers in other countries). Evenworse, if an error did slip through, the results could be disastrousfor the whole free software community. As long as the translationsare unofficial, they can't do any legal harm.

To underscore the fact that these translations are not officiallyvalid, we do not publish translations. To make that clear, we don'tpost them on gnu.org, or on other GNU and FSF web sites; we only linkto them.

Verbatim Copying and Distribution

The standard copyright terms for GNU web pages is now theCreativeCommons Attribution-NoDerivs 4.0 International License. It used tobe (and for a few pages still is):

Verbatimcopying and distribution of this entire article are permitted worldwide,without royalty, in any medium, provided this notice ispreserved.

Please note the following commentary about this“verbatim license” by Eben Moglen:

“Our intention in using the phrase ‘verbatim copying inany medium’ is not to require retention of page headings andfooters or other formatting features. Retention of weblinks in bothhyperlinked and non-hyperlinked media (as notes or some other form ofprinted URL in non-HTML media) is required.”

List of Free Software Licenses

  • List of Free Software Licenses

    If you are contemplating writing a new license, please contact theFSF by writing to<licensing@fsf.org>. Theproliferation of different free software licenses means increased workfor users in understanding the licenses; we may be able to help youfind an existing Free Software license that meets your needs.

    If that isn't possible, if you really need a new license, with ourhelp you can ensure that the license really is a Free Software licenseand avoid various practical problems.

What Is Copyleft?

Copyleftis a generalmethod for making a program freesoftware and requiring all modified and extended versions of theprogram to be free software as well.

The simplest way to make a program free is to put it in thepublicdomain, uncopyrighted. This allows people to share the programand their improvements, if they are so minded. But it also allowsuncooperative people to convert the program intoproprietarysoftware. They can make changes, many or few, and distribute theresult as a proprietary product. People who receive the program inthat modified form do not have the freedom that the original authorgave them; the middleman has stripped it away.

In theGNU project, our aim isto giveallusers the freedom to redistribute and change GNUsoftware. If middlemen could strip off the freedom, we might havemany users, but those users would not have freedom. So instead ofputting GNU software in the public domain, we “copyleft”it. Copyleft says that anyone who redistributes the software, with orwithout changes, must pass along the freedom to further copy andchange it. Copyleft guarantees that every user has freedom.

Copyleft also provides anincentivefor other programmers to add to free software.Important free programs such as the GNU C++ compiler existonly because of this.

Copyleft also helps programmers who want to contributeimprovementstofree softwareget permission todo that. These programmers often work for companies or universitiesthat would do almost anything to get more money. A programmer maywant to contribute her changes to the community, but her employer maywant to turn the changes into a proprietary software product.

When we explain to the employer that it is illegal to distribute theimproved version except as free software, the employer usually decidesto release it as free software rather than throw it away.

To copyleft a program, we first state that it is copyrighted; thenwe add distribution terms, which are a legal instrument that giveseveryone the rights to use, modify, and redistribute the program'scodeor any program derived from itbut only if thedistribution terms are unchanged. Thus, the code and the freedomsbecome legally inseparable.

Proprietary software developers use copyright to take away the users'freedom; we use copyright to guarantee their freedom. That's why wereverse the name, changing “copyright” into“copyleft”.

Copyleft is a general concept; there are many ways to fill in thedetails. In the GNU Project, the specific distribution terms that weuse are contained in the GNU General Public License, the GNU LesserGeneral Public License and the GNU Free Documentation License.

The appropriate license is included in many manuals and in each GNUsource code distribution.

The GNU GPL is designed so that you can easily apply it to your ownprogram if you are the copyright holder. You don't have to modify theGNU GPL to do this, just add notices to your program which referproperly to the GNU GPL. Please note that you must use theentire text of the GPL, if you use it. It is an integral whole, andpartial copies are not permitted. (Likewise for the LGPL, AGPL, and FDL.)

Using the same distribution terms for many different programs makes iteasy to copy code between various different programs. Since they allhave the same distribution terms, there is no need to think aboutwhether the terms are compatible. The Lesser GPL includes aprovision that lets you alter the distribution terms to the ordinaryGPL, so that you can copy code into another program covered by the GPL.

Licenses for Other Types of Works

We believe that published software and documentation should befree software and free documentation.We recommend making all sorts of educational and reference works freealso, using free documentation licenses such as theGNU Free Documentation License(GNU FDL).

For essays of opinion and scientific papers, we recommendeither theCreativeCommons Attribution-NoDerivs 3.0 United States License, or thesimple “verbatim copying only” license stated above.

We don't take the position that artistic or entertainment works mustbe free, but if you want to make one free, we recommendtheFree ArtLicense.