What evidence? What am I missing? Does someone have a link to the Flat UI icon he's referring to? The impression I got from his message is, Flat UI included a verbatim copy of the DN icon.
I think you misunderstand. I'm not arguing as to whether the Flat UI guys copied them or not, but like the larger argument, the icon he is putting forward as copied work is itself conceptually very similar to other existing icon work(s). As a designer I would be more than a little miffed if that design appeared if I had created the Noun Project's version and not openly licensed it.
If that is the case, it somewhat undermines the claim that the assets are fully owned by them or even that ownership can be so quickly claimed.
IANAL, but that's what I was told by a law student.
http://news.ycombinator.com/item?id=5332635
It's certainly not a verbatim copy or even close.