Mozilla Public License

Free and open-source weak copyleft license for most Mozilla Foundation software such as Firefox and Thunderbird The MPL license is developed and maintained by Mozilla, which seeks to balance the concerns of both open-source and proprietary developers; it is distinguished from others as a middle ground between the permissive software BSD-style licenses and the General Public License.

- Mozilla Public License

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Apache Flex

Software development kit for the development and deployment of cross-platform rich web applications based on the Adobe Flash platform.

Adobe Flex (old icon)

The Flex 3 SDK was released under the MPL-1.1 license in 2008.

Common Development and Distribution License

A screenshot of free and open-source software (FOSS): Linux Mint running the Xfce desktop environment, Firefox, a calculator program, the built-in calendar, Vim, GIMP, and VLC media player

The Common Development and Distribution License (CDDL) is a free and open-source software license, produced by Sun Microsystems, based on the Mozilla Public License (MPL).


Practice of granting the right to freely distribute and modify intellectual property with the requirement that the same rights be preserved in derivative works created from that property.

Copyleft symbol
The Creative Commons icon for Share-Alike, a variant of the copyleft symbol

Notable copyleft licenses include the GNU General Public License (GPL), originally written by Richard Stallman, which was the first software copyleft license to see extensive use, the Mozilla Public License, the Free Art License and the Creative Commons share-alike license condition, the last two of which being intended for other forms of intellectual and artistic work, such as documents and pictures.

Software relicensing

Applied in open-source software development when software licenses of software modules are incompatible and are required to be compatible for a greater combined work.

A screenshot of Manjaro running the Cinnamon desktop environment, Firefox accessing Wikipedia which uses MediaWiki, LibreOffice Writer, Vim, GNOME Calculator, VLC and Nemo file manager, all of which are open-source software.

The source code of Netscape's Communicator 4.0 browser was originally released in 1998 under the Netscape Public License/Mozilla Public License but was criticised by the FSF and OSI for being incompatible.

License compatibility

Legal framework that allows for pieces of software with different software licenses to be distributed together.

License compatibility for derived works and combined works of a developer's own code and externally developed open-source-licensed code (adapted from Välimäki 2005 )
License compatibility between common FOSS software licenses according to David A. Wheeler (2007): the arrows denote a one directional compatibility, therefore better compatibility on the left side than on the right side.

For example, software that combined code released under version 1.1 of the Mozilla Public License (MPL) with code under the GNU General Public License (GPL) could not be distributed without violating one of the terms of the licenses; this despite both licenses being approved by both the Open Source Initiative and the Free Software Foundation.


Practice of distributing software under two or more different sets of terms and conditions.

A diagram showing how the user interacts with application software on a typical desktop computer. The application software layer interfaces with the operating system, which in turn communicates with the hardware. The arrows indicate information flow.

Examples include the source code of Mozilla Application Suite and previously Mozilla Thunderbird and Mozilla Firefox, that have used tri-licensing under the Mozilla Public License (MPL) 1.1, GNU General Public License (GPL) 2.0 or GNU Lesser General Public License (LGPL) 2.1 before the latter upgraded to GPL-compatible MPL 2.0, making the tri-licensing unnecessary.


Free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation.

Firefox 100 on Windows 11
Firefox 100 on Windows 11
Screenshot of Phoenix 0.1 on Windows XP
The result of the Acid3 test on Firefox 17
Firefox 57 on macOS High Sierra
Firefox 96 on Arch Linux
Logo used for Iceweasel
Firefox mascot at the FISL16 (2015), Brazil
Usage share of web browsers according to StatCounter.
Logo of "Phoenix" and "Firebird" before being renamed as Firefox
Firefox 0.8–0.10, from February 9, 2004 to November 8, 2004
Firefox 1.0–3.0, from November 9, 2004 to June 29, 2009
Firefox 3.5–22, from
Firefox 23–56, from August 6, 2013 to November 13, 2017<ref>{{cite web|last=Martell|first=Sean|title=(Re)building a simplified Firefox logo|url=|work=Reticulating Splines|access-date=September 5, 2013|date=June 27, 2013|archive-url=|archive-date=July 2, 2013|url-status=live}}</ref>
Firefox 57–69, from November 14, 2017 to October 21, 2019
The 2011 Nightly logo, used to represent nightly builds of pre-alpha versions
The 2013 Nightly logo
The 2017 Nightly logo
The 2019 Nightly logo
The 2011 Aurora logo, used to represent an alpha release
The 2013 Aurora logo
The 2015 Developer Edition logo
The 2017 Developer Edition logo
The 2019 Developer Edition logo
Blue globe artwork, distributed with the source code, and is explicitly not protected as a trademark<ref>Mozilla Trademark Policy FAQ {{Webarchive|url=|date=April 7, 2013 }}: "What are the Mozilla Trademarks and Logos?". Retrieved November 2, 2006</ref>
The logo for the Firefox brand of products and services, as of July 2019. It appears as if the fox was removed, but this is not the logo for the browser itself.

Firefox source code is free software, with most of it being released under the Mozilla Public License (MPL) version 2.0.

Firebird (database server)

Open-source SQL relational database management system that "runs on Linux, Microsoft Windows, macOS and several Unix platforms".

The Firebird database engine and its modules are released under an open-source license, the Initial Developer's Public License (IDPL), a variant of the Mozilla Public License (MPL) version 1.1.

Mitchell Baker

Executive Chairwoman and CEO of the Mozilla Foundation and of Mozilla Corporation, a subsidiary of the Mozilla Foundation that coordinates development of the open source Mozilla Internet applications, including the Mozilla Firefox web browser.

Mitchell Baker at OSCON 2005
Baker in 2008

She was involved with the Mozilla project from the outset, writing both the Netscape Public License and the Mozilla Public License.


Open-source message-broker software that originally implemented the Advanced Message Queuing Protocol (AMQP) and has since been extended with a plug-in architecture to support Streaming Text Oriented Messaging Protocol (STOMP), MQ Telemetry Transport (MQTT), and other protocols.

The source code is released under the Mozilla Public License.