John Cowan jcowan at
Sat May 28 21:25:54 UTC 2005

Darius Blaszijk scripsit:

> I would like to ask you some information on the differences between GPL and
> MPL software. I have a project that is released under GPL license and I
> would like to use MPL libraries. Is this possible or do I have to use GPL
> libraries or switch to MPL?? Is there a resource on the net that point by
> point explains what the differences are between the two?? Which one is
> "better"  or "preferred"??

In the general case, the GPL and MPL are incompatible due to the
patent-related provisions of the MPL, so creating programs from arbitrary
GPL and MPL code is not possible.

The main difference between the two is that GPLed code can only be used in
GPL-licensed projects, whereas MPLed code can be used in projects under
other licenses as long as any direct modifications to the MPLed code
are released under the MPL.

However, if *all* the GPLed code in the project is written by you,
then yes, it is possible.  You release your GPLed code with a special
exception that says "It is permitted to link this code with the following
libraries", naming them, or else "It is permitted to link this code
with any code released under the Mozilla Public License version 1.1",
or some other version of this.

This will *not* work if you have accepted substantial contributions
(typically small patches do not count) from others under the GPL.

John Cowan  jcowan at
All "isms" should be "wasms".   --Abbie

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