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In computing, the Mozilla Public License (MPL) is an open source and free software license. Version 1.0 was developed by Mitchell Baker when she worked as a lawyer at Netscape Communications Corporation and version 1.1 at the Mozilla Foundation.^[1] The MPL is characterized as a hybridization of the modified BSD license and GNU General Public License.^[2]

The MPL is the license for the Mozilla Application Suite, Mozilla Firefox, Mozilla Thunderbird and other Mozilla software. The MPL has been adapted by others as a license for their software, most notably Sun Microsystems, as the Common Development and Distribution License for OpenSolaris, the open source version of the Solaris 10 operating system.

The license is regarded as a weak copyleft. Specifically, source code copied or changed under the MPL must stay under the MPL. Unlike strong copyleft licenses, the code under the MPL may be combined in a program with proprietary files which would otherwise be derivative works of the MPL code.^[3] For example, Netscape 6 and later releases were proprietary versions of the Mozilla Application Suite. For these Netscape releases, AOL Time Warner was also exercising the exclusive rights to proprietary versions that the Netscape Public License provided to itself.

The Free Software Foundation (FSF) considers the license a free software license, but "not a strong copyleft" one. However, "unlike the X11 license" the license has "some complex restrictions" making it incompatible with the GNU GPL. They urge people not to use the license because of this incompatibility unless the provision in section 13 of the MPL is exercised to provide the work under either the GPL or any other GPL-compatible license.^[4] The MPL is also approved as an open source software license by the Open Source Initiative.

The Mozilla Suite and Firefox have been relicensed under multiple licenses, including the MPL, GPL and LGPL.^[5]

• Common Development and Distribution License
• Sun Public License
• AROS Public License [6]
• SPL SugarCRM Public License [7]

1. ^ The Time 100: Mitchell Baker: The "Lizard Wrangler" (Marc Andreessen, Time, 18 April 2005)
2. ^ Andrew M. St. Laurent, Understanding Open Source & Free Software Licensing, pp. 62-63 (O'Reilly 2004).
3. ^  http://www.mozilla.org/MPL/MPL-1.1.html
4. ^  http://www.mozilla.org/foundation/trademarks/policy.html
5. ^  http://www.redhat.com/about/corporate/trademark/
6. ^  Free Software Foundation, Various Licenses and Comments about Them: Mozilla Public License, http://www.gnu.org/licenses/license-list.html#MPL
7. ^  http://www.mozilla.org/MPL/relicensing-faq.html

Free software Portal

• Mozilla Public License, version 1.1, plain text (mozilla.org)
• Annotated Mozilla Public License, version 1.1 (mozilla.org)
• MPL FAQ (mozilla.org)
• Promiscuous Source (GPL vs. MPL) (David Wallace Croft)
• Mozilla Relicensing FAQ (mozilla.org)
• List of OSI approved licenses