[LAD] GPL and plugins

[Albert Graef]

Paul Davis wrote:
> If [ ... ] ***WE BELIEVE*** they form a single program, which must be
> treated as an extension of both the main program and the plug-ins.

Well, this is a FAQ, not expert legal opinion. But according to the FSF
the intent of the license is that if A and B are linked together in the
same program (no matter how that happens, static or dynamic linking,
dlopen etc.) and B is GPL'ed then the combination A+B becomes a
"derivative work" and is thus subject to the terms of the GPL.

At least that's how I read the GPL FAQ. YMMV, but from what I've read in
various discussions, e.g. at license-discuss at opensource.org, I believe
that this interpretation is right, or at least the one intended by the
FSF. No idea whether this would stand up in court. In any case, as a
vendor who wants to distribute such a combination, I would either ask
the authors for explicit permission or seek legal advice.

> i don't believe that this is really the same thing. yes, this
> definitely the point of releasing a library under the GPL. but
> libraries are not plugins.

No, but if your plugin is provided in the form of a dynamically loadable
module, then according to the FSF it's to be treated just like a library
linked into your program. It doesn't matter whether the linking happens
at compile time or at run time.

Otherwise a commercial vendor could just turn GPL'ed libraries into
"plugins" and happily sell its non-free programs using those. That's
surely not the intent of the GPL.

Albert

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr.Graef at t-online.de, ag at muwiinfa.geschichte.uni-mainz.de
WWW:    http://www.musikinformatik.uni-mainz.de/ag