I would argue that very rarely, especially in this "global village" of ours, is any idea or design truly, uninspired originality. That being said, I'm not advocating that you cite the inventor of the colour red if you use it, but I think in the spirit of community based software and just in the interests of staving off some of these ludicrous notions of intellectual property and what-not, all of us who are displeased with seeing, say the boy scout having to pay a license fee to sing "happy birthday", should give credit where credit is due! Even if it is a completely, unrecognizable, the original author wouldn't even know it was his kind of re-design, I think offering a little credit is the "communal" thing to do, even something as discrete as a comment in the code somewhere.
I think copyrights and patents and what not are a good thing when used properly, as is open-source or communal 'property', in the non-open-source world, money is the citation per say, in non-commerce areas, its the acknowledgement, the idea that 'someone shared this with me and now I'm sharing their idea, with my own touches, with you'.
I however would be very pleased if someone where to assert a patent over snow, I've just been out shovelling and it's still snowing and there is so much already!! If this was especially off-topic or sounds a little too socialistic-utopian, even for me, just blame it on exhaustion, from shovelling the snow...lots of snow! :)