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Licenses: Types of licenses

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The GPL license

The GPL license is the most widely used license in the free software world. Among the set of free software licenses, it is generally considered to be the one that offers the most freedoms to developers.

Richard Stallman , in his fight against proprietary software, created the “GNU General Public License”, commonly known as the “GPL license”. This is based on copyleft , the legal mechanism just mentioned.

Thanks to this license, the author of a software ensures that anyone can use his product, for any purpose whatsoever. In addition, this license grants many rights to users:

  • the freedom to study a program thanks to its source code
  • the freedom to tweak it and tailor a program to suit their needs (or pay someone to do it)
  • the freedom to distribute copies of this program (in its original form or in its modified version)

From its inception, this license was of course in opposition to the spirit of companies that develop proprietary software. The terms and conditions of this license can be viewed on the GNU site.

There are other licenses that govern free software, but not all of them are compatible with the GPL license [ 1 ].

Free software licenses compatible with the GPL

The GPL has several variants that are compatible with it:

  • the LGPL (In its previous version, version 2, this license was called the GNU Library General Public License (Gnu Lesser General Public License), which is a little less restrictive from a copyright point of view since it allows the integration of non-free modules. The terms and conditions of this license can be found at www.gnu.org/copyleft/lesser.html . This license is not particularly recommended by the GNU Project (Consult at on this subject the article by Richard Stallman www.gnu.org/philosophy/why-not-lgpl.html .)
  • Guile’s license which consists of the GPL plus a special assertion giving permission to include non-free software.
  • A license dedicated to documentation

Here is a quick statement of the various free software licenses that are compatible with the GPL:

  • the X11 license: it is a free software license which is simple and permissive but which does not rely on copyleft . It is also the license of XFree86. Its terms and conditions can be viewed at www.x.org/Downloads_terms.html .
  • the Expat license: it is a license which looks like the X11 license: it is simple, permissive and not copylefted (Terms and conditions of the license www.jclark.com/xml/copying.txt ). It is sometimes called the MIT License.
  • the General Cryptix license: very similar to the X11 license (Terms and conditions of the license http://www.cryptix.org/LICENSE.TXT ).
  • the modified BSD license: it is similar to the original BSD license (The original BSD (Berkeley Software Design) license poses compatibility problems with the GPL license) in which the advertising clause has been withdrawn. It is a simple and permissive free software license, not copylefted (BSD License Terms and Conditions and its Derivatives www.xfree86.org/3.3.6/COPYRIGHT2.html#5 ).
  • Zope Public License, ZPL, version 2.0 ( www.zope.org/Resources/ZPL License Terms and Conditions ): This is a simple, permissive, non- copylefted free software license . “The modifications of each remain the property of their authors, but the Zope company would increasingly like to encourage common ownership, to ensure better control of the versions distributed” [ 2 ].
  • the World Wide Web Consortium (W3C) Software License ( License Terms and Conditions www.w3.org/Consortium/Legal/2002/copyright-software-20021231.html ).
  • the eCos license, version 2.0: it is a free license which incorporates the terms of the GPL but which authorizes links with other software not placed under the GPL. This license has the same weak points as the LGPL (See www.gnu.org/philosophy/why-not-lgpl.html ).
  • the Berkeley Database license, also known as the Sleepycat Software License (License terms and conditions www.sleepycat.com/docs/sleepycat/license.html )
  • the Intel open source license published by the OSI: the details of this license can be found on the site ( www.opensource.org/licenses/index.php ).
  • the Artistic License 2.0 and the Artistic License Clarified (see also www.opensource.org/licenses/index.php for more details).

In addition, there are several other free software licenses specific to software or companies, compatible with the GPL license, among which we can mention:

  • OpenLDAP version 2.7 license
  • Python licenses (up to version 1.6a)
  • Perl license
  • the Netscape JavaScript license
  • the Eiffel Forum license (from version 2)

Free software licenses not compatible with the GPL

Here is a quick statement of the various free software licenses that are not compatible with the GPL:

  • the original BSD (Berkeley Software Design) license ( www.xfree86.org/3.3.6/COPYRIGHT2.html#6 ): this is a simple and permissive free software license, but is not copylefted and it includes a “BSD advertising clause”, which causes, among other things, its incompatibility with the GPL license (see www.gnu.org/philosophy/bsd.fr.html ). The GNU Project strongly recommends against adopting the original BSD license.
  • Apache licenses (versions 1.0 and 1.1): these are simple and permissive licenses, not copylefted , which present practical problems similar to those of the BSD license ( www.gnu.org/philosophy/bsd.fr.html ). “The Apache license does not expressly authorize the integration of Apache components into a proprietary version, but neither does it prohibit it. “[ 2 ].
  • the Academic Free License version 1.1 ( opensource.org/licenses/academic.php )
  • the Open Software License version 1.0 ( www.rosenlaw.com/osl.html )
  • the Zope Public License, version 1 which presents practical problems similar to those of the BSD license ( www.gnu.org/philosophy/bsd.fr.html ).
  • xinetd license: the additional conditions it places on the redistribution of modified versions contradict the corresponding requirements of the GPL ( www.xinetd.org/license ).
  • om / developerworks / opensource / license10.html
  • the LaTeX Project Public License (LPPL): which notably requires that any modified file be renamed.
  • the Mozilla Public License (MPL) ( www.mozilla.org/MPL/MPL-1.1.html ): it is such that it is impossible to use modules under GPL license with a module under MPL license.

We could still cite many free software licenses that are not compatible with the GPL license:

  • the old OpenLDAP license (version 2.3)
  • Python licenses (from version 1.6b1, which is incompatible because it is subject to the laws of the State of Virginia)
  • the Vim license in version 5.7 (which recognizes the original project manager’s right to request a modified copy to be sent)

For further

For more details on the different licenses available to software designers, see the guide written by the French organization ATICA (Agency for Information and Communication Technologies in Administration) (now called ADAE (Agency for the Development of Electronic Administration).

In addition, the site www.opensource.org has a fairly extensive list of free software licenses ( www.opensource.org/licenses/index.php ).

Finally, in addition to these licenses which apply to software, there are also licenses intended particularly for documentation, such as:

  • the GNU Free Documentation License (FDL) detailed on the GNU project website www.gnu.org/copyleft/fdl.html
  • the FreeBSD Documentation License: Its terms and conditions can be found at http://www.freebsd.org/copyright/freebsd-license.html .
  • the Apple General Documentation License, version 1.0 or Common Documentation License ( www.opensource.apple.com/cdl ).
  • the Open Public License, version 1.0 ( opencontent.org/openpub ).

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