January 2012 was a milestone in FOSS licensing with the release of the Mozilla Public Licence (MPLv2) and its approval by the Open Source Initiative (OSI). Simon Phipps (OSI director) perceives it as more than a refresh, but as opening new opportunities for the unity of the open source community.
Indeed, using an approach pioneered in the European Commission's European Public License (EUPL), MPLv2 includes clauses that allow a project to optionally and explicitly declare compatibility with other licenses.
The MPL is widely interoperable:
- A larger work (including the software covered by the MPLv2) may be distributed under any licence (but in such case, the specific MPLv2 requirements must stay applicable to the component of the larger work which is the covered software).
- A larger work may also be distributed (including the component that was covered by the MPL v2) as a whole under a “Secondary Licence”, meaning currently “the GPLv2, LGPLv2.1, AGPLv3 and later versions of those”.
As a result, the MPLv2 is more permissive than the EUPL, because a larger work may be distributed under any licence, while the EUPL limits such distribution to a few licences excluding source code appropriation (one of the EUPL basic requirements was to avoid the risk of paying again for software originally developed with public money).
However, permissive licences have their own merits (to be more business friendly) and the MPLv2 – which is interoperable with the EUPL (meaning that you may include a MPLv2 component in a larger application distributed under the EUPL) marks a clear progress towards interoperability.
It satisfies the extremists of neither world, Simon Phipps says, but pragmatically provides corporate-backed open source projects with a new approach. They can have a community that sustains permissively licensed code while also providing that community a way to relate to other communities with copyleft-licensed code.
The list of secondary licences is imbedded in the MPL (in the initial definition section), while publishing the list in an annex (like the EUPL does) could facilitate evolution.
The list of secondary licences does not mention the GPLv3 as it may (based on the name) be seen as a later version of the v2, but well the AGPLv3 (which is a GNU variant covering also the online distribution of “software as a service” as the EUPL does).
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