The difference is that the code is distributed for free. No judge is going to award damages for the redistribution of something that is free. At least, not actual damages, like $$$ per infringing copy. The breach of the terms (like not redistributing the source code) could be translated to some punitive damages, perhaps.
I don't see how the lack of a monetary cost for _one_ of the licensing options should affect awarding damages.
Probably the best outcomes you can hope for are: the violator of the license is either asked to stop distributing the software, or else to come into compliance: replace the GPL'ed part with a from-scratch workalike, so that the program is no longer distributed with any GPLed code, or else make the whole program GPLed.
You forgot the third option in this case. If Ximpleware is open to it, they could pay for a commercial license.
Sure, but a programmer that doesn't know CSS is pretty limited!
A _web developer_ maybe, but a _programmer_ surely isn't.