Here's the full deal:

If you store your screenshot on English Wikipedia, non-free imagery is allowed when there's a rationale, which in this case would be "fair use". That's the decision of that community. I think you could store that screenshot as is. http://en.wikipedia.org/wiki/Category:Fair_use_screenshots

If you use Wikimedia Commons (a common media backend for all the Wikipedias and other projects), there are no exceptions; it's all free, all the time. Fair use is NOT allowed. The guidelines are here: http://commons.wikimedia.org/wiki/Commons:Screenshots

On Commons, in theory, title bars and other OS windowing widgetry are okay if and only if it's a fully open source operating system.

In practice, most Commons volunteers are not insane, and don't care. I don't know of any case where Microsoft has sued someone for a screenshot that included a title bar, where there was no intent to deceive people or otherwise misuse their work.

But, Wikipedia and Wikimedia Commons tend to attract and enable a kind of person that values extreme consistency and rule-following over all other considerations. Someone who makes it their mission to eliminate all screenshots with titlebars probably won't be reined in.

I've had images with them included deleted before, which is why I modified the golly screenshot. To be perfectly honest, I'm not sure what's allowed, and I doubt many people who are not active commons contributors do, either.

Some editors went through and deleted a massive number of useful Mac/Windows screenshots several years ago, but I don't think there's ever been an actual policy stating these screenshots were a legal issue.

Also, the GPL only covers code, not program output (under normal circumstances), so I don't see how it applies to screenshots anyway.

>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 doesn't matter, the application of the "rules" (read: guidelines) is so arbitrary and capricious as to be entirely meaningless and unpredictable.