MPL
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| MPL | |
|---|---|
| Name | MPL |
| Author | Mozilla Foundation |
| Initial release | 1998 |
| Latest release | 2.0 (2002) |
| License | Permissive |
| Website | Mozilla Foundation |
MPL
The Mozilla Public License is a source code license created to balance open collaboration with proprietary development. It was drafted and published by the Mozilla Foundation to govern contributions to projects originating with the Netscape Communications Corporation codebase and later used by projects involving the Mozilla Corporation, Mozilla Foundation, and allied projects. The license occupies a middle ground between GNU General Public License-style copyleft terms and more permissive terms like those used by the Apache License and MIT License.
Overview
The license was introduced alongside early releases of the Netscape Navigator source and served as the governing instrument for the Mozilla Application Suite and subsequent projects such as Firefox and Thunderbird. It defines obligations for distribution, modification, and application of changes to files containing covered code while permitting linking with code under other licenses, including proprietary terms used by companies like Microsoft and Apple Inc.. The text of the license focuses on file-level reciprocity, allowing redistribution of modified files under the same terms while enabling the combination of covered files with differently licensed components, as practiced in projects such as SeaMonkey and Bugzilla.
History
The license emerged during legal and organizational debates following the release of the Netscape Communications Corporation source code in the late 1990s, a period marked by interactions with entities like Sun Microsystems and discussions within standards bodies such as the Internet Engineering Task Force. Early stewardship involved stakeholders from the Mozilla Foundation and contributors drawn from corporate partners including IBM, Red Hat, and Google. The MPL evolved from its original 1.0 form into successive drafts culminating in a major revision that sought to address compatibility with the GNU General Public License and clarify patent provisions, leading to the widely adopted 2.0 revision. The 2.0 update was informed by precedents set by licenses such as the Apache License and community discussions involving organizations like the Free Software Foundation and the Open Source Initiative.
Licensing and Versions
MPL 1.0, 1.1, and 2.0 represent the principal published versions, with 2.0 explicitly designed for greater interoperability with licenses used by projects at Google and IBM and for compatibility with the GNU General Public License under certain conditions. The license permits redistribution of source and object code, imposes obligations to make modifications available when distributed, and contains patent language influenced by agreements similar in aim to those in the Eclipse Public License and the BSD licenses. Corporate adopters such as Cisco Systems and Oracle Corporation have considered MPL terms when contributing to projects like Thunderbird or integrating Netscape-derived components into commercial offerings.
Key Features and Components
The license specifies that modifications to covered files must be disclosed under the same terms, creating file-level copyleft that contrasts with the project-level copyleft of the GNU General Public License and the permissive approach of the MIT License and the BSD licenses. It includes provisions addressing patents, attribution, and notice requirements similar to language found in the Apache License. The MPL also defines compatibility mechanisms enabling relicensing portions of a larger work to align with the GNU General Public License when prerequisites are met, an aspect relevant to collaborations involving projects like LibreOffice and Chromium. Entities such as Mozilla Corporation and contributors from Red Hat and IBM have relied on these components to structure contribution policies and corporate participation.
Adoption and Use Cases
The license has been used by numerous projects originating with the Mozilla Foundation including Firefox, Thunderbird, SeaMonkey, and server-side projects maintained by organizations like Mozilla Corporation and community groups. Other adopters include standalone projects and companies that required a middle-ground license permitting proprietary aggregation while protecting source-file contributions, examples being initiatives from Adobe Systems and smaller open-source communities such as those surrounding Bugzilla derivatives. The MPL has been chosen in contexts where interoperability with proprietary toolchains from vendors such as Microsoft and Apple Inc. was desirable, and where participation from corporate contributors including Google or IBM was expected.
Reception and Criticism
Observers including the Free Software Foundation and advocates tied to the Open Source Initiative have debated the license’s strengths and weaknesses, praising its pragmatic balance but criticizing its file-level reciprocity for potential ambiguity compared to the stronger copyleft of the GNU General Public License. Legal commentators and corporate counsel at firms like Red Hat and Oracle Corporation have analyzed the license for patent safety and compatibility with corporate contributor agreements; some recommended clarifications that influenced the 2.0 revision. Critics from projects preferring maximal permissiveness, such as proponents of the MIT License or the BSD licenses, argue that the MPL’s obligations can complicate inclusion in entirely permissive codebases, while proponents highlight successful long-term deployments in Mozilla projects and corporate collaborations.