Mozilla Public License

Mozilla Public License. The Mozilla Public License is a free and open source software license developed and maintained by the Mozilla Foundation. It is characterized as a weak copyleft license, aiming to balance the freedoms of open collaboration with the practical needs of commercial software development. First introduced for the Netscape Navigator source code, it has become a widely adopted license for a diverse range of software projects beyond the Mozilla ecosystem.

History and development

The license was originally crafted in 1998 by Mitchell Baker and the legal team at Netscape Communications Corporation during the historic release of the Mozilla Application Suite source code. This event was a pivotal moment in the open-source software movement, following the earlier successes of the GNU General Public License. The creation of this license was a direct response to the complexities perceived in the GNU General Public License, particularly for use by corporations. The initial version was subsequently revised with input from the Free Software Foundation and the broader community, leading to the release of version 1.1. The driving force behind its development was to establish a legal framework that could foster a collaborative community, as seen with the Apache HTTP Server, while being palatable to entities like IBM and Apple Inc..

License terms and conditions

The license grants users the rights to use, study, share, and modify the software. Its core weak copyleft provision requires that modifications to files originally covered under it must remain under the same license, but it permits those files to be combined with separate, proprietary files into a larger work. This distinguishes it from the strong copyleft approach of the GNU General Public License. Key conditions include the requirement to make the source code of any modified files available and to detail changes in an accompanying file. It also includes a patent retaliation clause, similar to provisions in the Apache License 2.0, which terminates patent grants from a contributor if they initiate patent litigation against the project.

Compatibility with other licenses

A primary design goal, especially for version 2.0, was to improve compatibility with other major open source licenses. It is explicitly compatible with the GNU General Public License, Apache License 2.0, and the GNU Affero General Public License. This means developers can create a combined work using code under these licenses, which can then be distributed under the terms of the compatible license. This interoperability was a significant advancement over earlier versions and has been welcomed by projects like the Linux kernel community and foundations such as the Apache Software Foundation. However, combining it with code under strong copyleft licenses like the original BSD licenses requires careful legal review.

Usage and adoption

Beyond its flagship use for the Firefox web browser and the Thunderbird email client, the license has been adopted by a wide array of significant projects and organizations. Notable adopters include Adobe Systems for parts of the Adobe Flex framework, the Eclipse Foundation for certain runtime components, and LinkedIn for various open-source tools. Its business-friendly terms have made it a popular choice for dual-licensing strategies employed by companies like Qt Group and for libraries that wish to be used in both open-source and proprietary products, a model also seen with the MySQL database.

Versions and evolution

The license has undergone two major revisions. Version 1.0 was the original release with the Netscape code. Version 1.1, released in 1999, included clarifications and minor improvements. The most significant update is version 2.0, released in 2012 after a lengthy community process led by the Mozilla Foundation. This version simplified the text, enhanced compatibility with the GNU General Public License and Apache License 2.0, and modernized the patent provisions. The evolution from MPL 1.1 to 2.0 reflects lessons learned from decades of open-source development and legal challenges encountered by projects like OpenOffice.org and the Free Software Foundation's own licensing efforts.

Category:Free software licenses Category:Mozilla licenses Category:Open-source licenses Category:Software licenses