Relicensing from GPL v2 to LGPL v2 - What if I can't contact all contributors?

Question

I am a contributor to a very old project presently in violation of the GPL. Our project is a plugin for a closed-source program, but the GPL does not permit this kind of linking. The project should have been licensed under the LGPL instead, but the original authors were not aware of this.

There are only about 30 contributors to the project, but it's almost ten years old at this point; Many of these people have moved on and I'm not sure I can find them all.

How should I proceed with relicensing the project if I can't contact everyone?

Answer 1

You need all the copyright owners' permission to change license.

There's no natural GPL-implied path here because LGPL is more permissive. It allows redistribution of unmodified binaries without the offer of source, explicitly disallowed by GPL. This makes it moderately incompatible in this direction (but you could include LGPL in a GPL work).

So in order to distribute it under a different license, you need permission from either:

• The copyright owners (all of them).
• An agent who operates the copyright on behalf of the owners (all of them).
• Somebody with explicit permission to redistribute and sublicense under the terms you require.
• Some fancy combination of the above.

If you can't get suitable explicit permissions, you have to replace their work. This could be quite simple (if they all did whole blocks that could be replaced from fresh without needing to look at them, ie a clean-room implementation), but equally, it can mean awfully painful bisects that make the process more legally dubious. It might be a good prompt to extract the best parts and rewrite.

That said, this is civil law and you only have to answer to these people or their agents. A best-effort to contact them, followed by a best-effort to remove their code will be seen by most as a honourable attempt to do the right thing.

---

Just as a sidebar, the FSF isn't quite as adamant you need to move to LGPL:

If the program uses fork and exec to invoke plug-ins [...] there are no special requirements.

If the program dynamically links plug-ins, [...] that combination [...] would violate the GPL. However, you can resolve that legal problem by adding an exception to your plug-in's license, giving permission to link it with the non-free main program.

You still have a licensing issue that requires everybody's input, but it might be a smaller step to leave the existing license in place and add an additional excepted license for the application you want to link into it, extra-GPL.

Answer 2

Step 1: document the situation. Put up a notice that explains the problem; but be clear, not alarmist. As discussed on other questions, there's no problem for users of your plugin, only for people who would want to distribute a combined work of your plugin and the host.

Step 2: Survey the contributions of the unreachable individuals. Perhaps they are very small? This might either make them easily replaceable, or not big enough to copyright.

Step 3: Survey the mailing list archives. If there's a clear intention to allow this usage, then you might conclude that it's safe to change the license (by adding a permissive term or by switching to LGPL) on the grounds that you have evidence that all the copyright holders intended this in the first place.

HOWEVER: You've noted in other questions that you incorporated code from other GPL sources. You can't relicense that without permission from its copyright holders, so there's really no point to changing your license unless you can replace that code.

To repeat what I have written elsewhere: You and your fellow contributors have not violated anything. You have, however, created an opportunity for a very small group of people to violate the license of the GPL code you incorporated. If there is no realistic situation in which anyone would want to distribute a combined work, then this is more humorous than disastrous. Your notice would consist, more or less, of:

Hey, we used the GPL and we forgot to add a dynamic linking exemption, and we incorporated some other GPL code that has no dynamic linking exception. If you are an end user, this makes no difference to you. The GPL gives you all the rights you need. Our mistake only matters if you want to create a derived work by combining our plugin with <INSERT APPLICATION NAME HERE> and distribute that combined work. In that case, we're really sorry, but we can't guarantee that some copyright holder won't call you out for a violation, so we have to tell you that this would be a very bad idea.