Well when animals enter PS i really want a cat or a bird if its possible and goddamn it if some licence is gonna stop me from taming a little wild black cat. It would really suck if i would have to have a licence to have a cat a dog or whatever. also it would be unrealistic!
Maybe it would be alright to require a licence for a dragon or something, but for a dog, horse, cat, bird, rat, bunny, bat, butterfly, beetle, cow, goblin, chicken, camel, snail, donkey, pig, worm and so on it would be crap! However i think that a limit of two tamed creatures would be good because of lag.