Let's put it this way. If it were a fake company, wouldn't one of the big media sites have uncovered that fact by now? It's not a hard thing to find out.
As for the game itself, they announced various publishers by name and even claimed their game will utilize the Gamebryo engine. If none of this were true, all those parties would have right to sue them for illegally using their name for publicity or if nothing else would have spoken publicly against their claims.
On the contrary, Emergents CEO (developers of the Gamebryo engine) have spoken on behalf of Nibris about Sadness already.
"From the early stages of pre-production with Sadness, Nibris realized that they would need development technology that allowed for an extreme amount of flexibility in the creative process, which is a cornerstone of the Gamebryo framework," said Geoffrey Selzer, CEO of Emergent.