Complex sentence: Monolith focused on the development of the PC, PlayStation 4 and Xbox One versions, while the development of the PlayStation 3 and Xbox 360 versions was outsourced to Behaviour Interactive, and the port to OS X and Linux was done by Feral Interactive.
Split into simpler sentences: Monolith focused on the development of the PC, PlayStation 4 and Xbox One versions, while the development of the PlayStation 3 and Xbox 360 versions was outsourced to Behaviour Interactive. The port to OS X and Linux was done by Feral Interactive.