Looks like the pitchforks are out over on HN.
It was pretty straightforward. Our reaction was "Cool, a flat UI theme" to "Wait, this looks familiar" to "Wait, are those our illustrations?".
I contacted the designmodo people over email, because that's the right way to handle this. The owner was being stubborn at first and refused to admit wrongdoing. At that point, I submitted the DMCA request. Eventually, he removed the most blatant icons which (in my eyes) is an admission of guilt.
They even managed to kinda lift the old DN icon :) http://imgur.com/3zoKuvH
If you have some intimiate knowledge of LayerVault's UI (which their designer apparently does), the similarities are a bit more than striking. That's not a huge issue until you release everything together - the icons, the colors, the UI elements, whatever.
We give a lot of our stuff away for free. We put a lot of our projects on cosmos.layervault.com, we write about interesting concepts we've come up with and include the code on our blog, whatever. This isn't about thinking we own "Flat Design" or being mad that there's some other design out there with a similar aesthetic.