Well this is a blooming mess. The Fun Pimps, developers of 7 Days to Die, have been hit with a DMCA notice, their Greenlight page has been taken down and they are now in a legal tango with Tripwire Interactive, creators of Killing Floor. All this appears to be down to communication problems, with both The Fun Pimps and Tripwire Interactive being victims.
One of Tripwire's models from Killing Floor was stolen, repainted and sold as an original asset on the Unity Store. While purchasing placeholder assets for 7 Days to Die, The Fun Pimps purchased the stolen model and use it in the game. Tripwire's lawyer - who calls himself a pet pitbull - got Steam to take down the 7 Days to Die Greenlight page after the developer discovers the stolen asset in game, and now the only person not suffering is the thief.
The Fun Pimps intend to remove the stolen asset in an upcoming update. According to Tripwire's lawyer - the so-called pet pitbull who calls the thief a "dick" - claims that his client contacted The Fun Pimps and requested that they remove the asset, which they promised to do, but apparently never did.
Though The Fun Pimps purchased the model through the Unity store and are as much victims of the thief as Tripwire is, Tripwire's lawyer is taking aggressive measures, stating that he has a "bunch of real deal nastiness" in his "legal bad of tricks".
Hopefully this debacle can get cleared up as soon as possible without more problems for either developer.