Well, that remains to be seen. Looking at both websites, it's difficult to tell what they are talking about. Flat-UI doesn't seem to have any assets that mirror anything on LayerVault's. They need to be more specific.
> Flat-UI doesn't seem to have any assets that mirror anything on LayerVault's.
I would say that is the issue in a nutshell. LayerVault is claiming they are the exclusive rights-holders, yet absolutely nothing in Flat-UI is the same as anything on LayerVault's public site.
The only possible angle remaining would be if LayerVault had a bunch of these elements behind their paywall... something tells me that's not the case.
Edit: Alright, I admit the colour Turquoise is used on both pages. Still, I'm fairly confident turquoise boxes (of differing shapes!) are not copyrightable.