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Published software should befreesoftware. To make it free software, you need to release itunder a free software license. We normally use theGNU General Public License (GNU GPL),but occasionally we useotherfree software licenses. We use only licenses that are compatiblewith the 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.
A number of our licenses are currently being revised, and we welcome yourcomments on the proposed texts. Please visithttp://gplv3.fsf.org to read the currentdrafts and participate in the process.
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 GNU Lesser General Public License is used by a few (not by any meansall) GNU libraries.
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 noncommercially.
Legally speaking, the original (English) version of the GPL is whatspecified the actual distribution terms for GNU programs. But to helppeople better understand the licenses, we give permission to publishtranslations into other languages provided thatthey follow our regulations for unofficial translations.
The standard copyright notice for GNU webpages reads:Verbatim copying and distribution of this entire articleare permitted worldwide without royalty in any medium providedthis notice is preserved. Please note the followingcommentary by Eben Moglen:
"Our intention in using the phrase `verbatim copying in any medium' isnot to require retention of page headings and footers or otherformatting features. Retention of weblinks in both hyperlinked andnon-hyperlinked media (as notes or some other form of printed URL innon-HTML media) is required."
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.
Copyleft is a general method 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 (18k characters), uncopyrighted. This allows people toshare the program and their improvements, if they are so minded. Butit also allows uncooperative people to convert the program intoproprietarysoftware (18k characters). They can make changes, many or few,and distribute the result as a proprietary product. People whoreceive the program in that modified form do not have the freedom thatthe original author gave them; the middleman has stripped it away.
In theGNU project, our aimis to giveall users the freedom to redistribute and changeGNU software. 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 contributeimprovements tofree software get 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 it but 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 and the 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.
We believe that published software and documentation should be free 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 recommend thesimple "verbatim copying only" license that is used for this web page.
We don't take the position that artistic or entertainment works mustbe free, but if you want to make one free, we recommendtheFree ArtLicense.
Please send FSF & GNU inquiries tognu@gnu.org.There are alsoother ways to contact the FSF.
Please send broken links and other corrections (or suggestions) towebmasters@gnu.org.
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Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
Verbatim copying and distribution of this entire article ispermitted in any medium without royalty provided this notice is preserved.
Updated:$Date: 2007/11/11 09:52:01 $
