Re: Plugins, libraries, licenses and Debian

[mru@kth.se (Måns Rullgård)]

Arnoud Engelfriet <galactus@stack.nl> writes:

>> >> OK, say I use the X11 license.  Now suppose someone installs a closed
>> >> source plugin.  Suppose it also happens that this same user has
>> >> installed some GPL plugin.  Both plugins would be allowed separately,
>> >> right?  When the user runs the program, it will load both plugins.
>> >> Would this in some magical way make the plugins derived works of each
>> >> other, thus violating the GPL?
>> >
>> > No. But a vendor could get into trouble if they shipped both.
>> 
>> How's that?  The GPL allows distribution together with non-GPL works,
>> as long as the non-GPL things are not derived from anything GPL'd.  In
>> my opinion, placing two shared objects in the same tar file doesn't
>> make one a derived work of the other.  Would it make a difference if
>> the offending (to rms) plugins were distributed separately?
>
> The FSF seems of the opinion that a program that uses a
> library is a derivative work of the library, because
> at runtime the two are combined.
> http://www.gnu.org/licenses/gpl-faq.html#IfLibraryIsGPL
>
> It seems logical that they are of the same opinion regarding
> plugins. 

I've read the GPL FAQ and the twisted logic therein.  I can somewhat
follow the argument as it applies to shared libraries, but strictly
speaking, the combination of program and library only exists in the
RAM on the computer, and is never distributed (unless someone
distributes core dumps).  Still, I can accept the argument that the
program is tied to the library, even before linking, and thus should
be considered a derived work.

When it comes to plugins, I have to disagree with the FSF.  If I write
a program and release it under some non-GPL licencse, and *later*
someone writes a plugin and releases it under the GPL, how can the
program possibly become a derived work of that plugin?

In my particular case, a plugin must implement one or more predefined
interfaces.  Several implementations of an interface can (and do)
exist independently.  Does this affect the situation in any way?

BTW, what is the FSF's position on programs communicating using
CORBA-like methods?

-- 
Måns Rullgård
mru@kth.se