I had to tell that gobbo with the chase, that I don't want to participate. After that the owlbear ran across the courtyard and I approached it with Speak with Animals and told him to go to my camp. It made clear, that I had to kill the goblins in the courtyard first, so I did that. Be careful with AoE spells, since you can kill the cub with it.
I think, there is a possibility to buy the owlbear from the goblin with the chasing game, but I haven't had that option.
