Hi,
I would say that it's not a Gorrilla crab, as it has a large smooth carapace and smaller legs which appear more compacted to the body.. IMO i would say freindly, but its very hard to say. Most crabs in the long term become predatory as they fight for food. Best to keep him in the sump or give to a collector who keeps crabs
Try feeding it meat (Krill) and algae at the same time to see if it is a carnivore
Simon.