It is rumored that PlayStation 4 runs an optimized version of FreeBSD 9.0, as its OS. There isn’t any official information on this topic, but since PlayStation 3 had an option called OtherOS, that allowed the user to run Linux, why not run FreeBSD on PS4?
From this printscreen, leaked in the press, we can see that PS4 runs on Orbis OS (if only this picture was taken to a PS4 boot menu), which is a derivate of FreeBSD 9.0:
