The Mozilla Public License 1.1 is not compatible with (any version of) the GPL – that is, you cannot put MPLed code into a GPLed binary. The alpha 3 draft of the MPL 2 has opt-in GPL compatibility which can only be chosen at the time the software is first licensed (section 11.2).
I personally believe that most or all groups who are currently licensing their software under the MPL (only) would not mind, or actively desire, GPL compatibility, and the new MPL should give them the opportunity to choose it. I think most free software developers see licensing as a pain, and license incompatibility as a double pain, and would much rather everything were upwardly compatible with everything else.
To test this belief, and so we can appropriately publicize the new version of the MPL when it comes out, I am creating a list of MPLed projects. If you know of an MPLed project please add it to the list. And I want to hear from those projects as to whether they are opposed to, in favour of, or indifferent to, GPL compatibility for existing projects being put into MPL 2. Have a discussion on your mailing list and let me know the outcome.
Particularly if you or your project chose the MPL specifically because it is GPL-incompatible, please contact me. I will treat your response in confidence if you wish.
I’m also looking to make a list of GPLed projects using MPLed libraries (with a GPL exception of some sort – or even without!). That list is at the bottom of the same wiki page. If you are a GPLed project and wanted to use MPLed libraries but couldn’t, I want to hear from you too.
Please spread the link to this blog post throughout the free software community – I want to make sure I’ve reached as many MPL-using projects as possible.
Note: this canvassing of opinion is not official and is not binding in any way on the MPL 2 drafting team.