>the GPL only covers code, not program output (under normal circumstances), so I don't see how it applies to screenshots anyway.
It's an interesting question. The drawing of the window is, I would argue, indistinguishable from the code. It's like saying the HTML, CSS, and images on a site are GPL'd, but screenshots aren't. The rest of the program output is merely algorithmic, and thus not subject to copyright.
This discussion is wandering off into la-la land. The GPL isn't designed to cover things like websites or bitmapped images. There's other 'free' content-oriented licenses which should be used instead.
It's an interesting question. The drawing of the window is, I would argue, indistinguishable from the code. It's like saying the HTML, CSS, and images on a site are GPL'd, but screenshots aren't. The rest of the program output is merely algorithmic, and thus not subject to copyright.