Check what the framework developer said: https://github.com/github/dmca/commit/735e17614cca63102b8414...
"he said that he: "I am the exclusive rights holder for the artwork contained within Flat UI". Liar!."
1) None of the illustrations in Flat UI are identical to LayerVault's illustrations. Derived works? Maybe. But under the law, that's okay.
2) Looking at illustrations from the Noun Project, and color palettes from Google and elsewhere, we see the same similarities that we do between LayerVault and Flat UI. If Flat UI is guilty of copyright infringement as LayerVault asserts, then LayerVault is most certainly guilty of copyright infringement from elsewhere.
3) Copyright isn't even the right legal vehicle for this debate. LayerVault could conceivably deem its icons to be trademarks, and show a likelihood of confusion when compared to Flat UI's icons. But LV using an icon set as a trademark would be unprecedented, and difficult to argue. (And even if that were the case, the Noun Project could just as easily claim LV infringed on their trademark.)
Overall, if LayerVault is claiming they own the copyright to illustrations used in Flat UI, they're flat-out wrong. And that's where the problem comes in - filing a fraudulent DMCA notice is bad business.
And http://i.imgur.com/qJXJUaH.png are just proofs than they can't own anything.