"RMS has written an article explaining how the GPL is applied in programs using plug-ins like Photoshop or the GIMP. His article can be found
Apparently it is illegal to write a GPLd plug-in to
a non GPLd program if they link in the same code (or am I really misunderstanding
Andy wrote back saying that Gimp
plug-ins etc don't count 'cut they are seperate executables. If someone
has a few examples of what plug-ins would theoretically apply
here, send them my way.