I agree on that. I mentioned the colors, becaue the parent comment said that it was only about 3 similar looking icons. The DMCA takedown request senders thought there's more to it.
It's true that all these flat UI themes are really similar, so It's really interesting how this will turn out and will the Flat UI repo will be brought back.
However in order to win an infringement claim you'd have to show that they constituted a substantial part of a work and that the colours were copied and not derived from a third party source or coincidentally the same. The usual civil law test is the balance of probabilities.
I think a more likely claim is that the matching colour scheme were a trademark infringement, an unlicensed use of trade dress (jurisdiction dependent of course). AFAIK DMCA takedown notices don't work for trademark infringement though?
If we look at Webdings (http://en.wikipedia.org/wiki/Webdings - TrueType dingbat font developed in 1997), there's actually a newspaper icon there that looks a lot like all of these:
Thanks for posting this--I hadn't seen the side by side comparison. If this is what's being claimed as 'copies' of their artwork, then it's clearly an empty claim. The Flat UI icons look better, to my taste.
http://imgur.com/IH1osAD