It seems as if he is always playing. You are there trying to change his diaper and he is trying to get up to run away so you can run after him. He's always playing. I am not worried yet, in fact it's very pleasant.

Sometimes you just have to play so you don't get bored. You know a cranky bored baby just then might turn into a bored and fussy baby, we don't want that now do we? :)

So long as he's playing while you're changing his diaper and not playing in his changed diaper it sounds ok to me. I've seen too many kids who simply won't stay still and turn into terrors as they get older. Playing all the time sounds like a fun alternative.