Mozilla Projects and GPLed Code

I had two emails about this yesterday, so I thought I’d stick a post on Planet to clarify.

The short version: GPLed code may not be included in software that Mozilla ships.

The long version:

Three major goals of the Mozilla licensing policy are:

  1. legal simplicity for downstream users;
  2. the ability for as many people as possible to use our code in their products; and
  3. striking a balance between maintaining copyleft for our code, and the right of those downstream users to combine our code with proprietary code.

The practical result of this is that we act to preserve the right of anyone taking all or part of a codebase from us to use it under the terms of the MPL (currently mostly version 1.1, soon to be version 2), or in projects under the LGPL or the GPL, at their option. That means that all the constituent parts have to be under either the MPL 1.1 tri-license, or the MPL 2 without the incompatibility clause, or a simpler subset of those terms, such as Apache, BSD or MIT.

If any part was solely under the GPL, then people wanting to use MPL terms for the entire application could not do so – only GPL terms would be available, unless the GPL-only part was removed. It would also no longer be possible to release binary versions of e.g. Firefox under the MPL, as Mozilla does today.

If any part was solely under the LGPL, then people would not be able to use MPL terms for that part. This is possibly less of a problem, particularly if the software is a clearly-defined and self-contained library. There is some talk of changing the policy to permit LGPLed libraries to be included, but it’s at an early stage and no decision has been made yet. We would need to do some legal work to find out what the additional compliance requirements were on us and on users of our code, and whether it was possible to clearly identify what was part of the LGPLed library and what was not (both in general and in any particular case).

If an author of some code has placed it under the GPL, then that means that they want it to be used only in GPLed projects (and Mozilla projects are not GPLed projects). We need to respect that licensing decision that the author has made. There is a load of code out there which is unavailable for use by us at Mozilla. The fact that you can read the source, or use it in other projects doesn’t change that.

The release of the new MPL 2 does not change any of this.

So, if you want to use some code which is under the GPL in a Mozilla project codebase, you have a few options:

  • You can ask the licensing team to contact the author or authors of the code and ask them to make it available under the MPL or another licence which fits with
    our licensing policy. Software authors are often receptive to polite requests of this type. We have done this before for large pieces of code, e.g. cairo.

  • You can find another library implementing the same functionality. For many standard libraries, there is a GPL version and a BSD version.
  • You can rewrite the code (just as you would have had to do if you hadn’t found the library or if it had been proprietary or otherwise not open source).

Note also that I talk about “code that Mozilla ships”. We have a small number of internal tools, such as build tools, which were sourced from elsewhere and are GPLed. So finding GPLed code in a Mozilla repo is not necessarily a violation of this policy. However, “software that we ship” includes anything we create ourselves as an open source project, even if it’s primarily for our own internal use (e.g. the AMO codebase). And this policy applies to all code being created under the auspices of the Mozilla project, whether the code is stored in a Mozilla-hosted repo or somewhere else, like GitHub.

One thought on “Mozilla Projects and GPLed Code

  1. Mozilla Firefox/Thunderbird/SeaMonkey do not make use of the additional copyleft relaxations the MPL allows to have over the GPL, so they could theoretically also ship as GPL-only in their current form, is that right?
    Then which software out there makes use of the possibilities of the MPL? Frontmotion Firefox? The bundled Firefox versions (with Yahoo toolbar, Bing toolbar, …)?