There was already a copyright on It's A Wonderful World. I think it was a movie or something. Squenix couldn't afford those copyright issues, I guess.
Probably because they were too busy milking money from FF7 sequels.
Well actually you can't hold copyrights on titles for things forever and sometimes not even at all. You see all the time that books and movies that aren't related to each at all have the same title. When a studio buys the rights to something to remake it, they are buying the intellectual property of the movie itself and not the title. I think this gets sticky when you are dealing with a franchise though. I imagine that they changed the title to something they assumed had better context in English and was closer to the context of "it is a wonderful world!" in Japanese and that there were no such copyright disputes.
But maybe I am an idiot and am completely wrong!
Anyway this game looks pretty retarded. =\ I guess I am on the
I hate ugly and gaudy things train so the game's graphic style really does not resonate with me and aside from that the gameplay sounds like a clumsy, stupid mess. Also I think this is the only case in history where game reviews consistently rate the game higher than user reviews at review sites and aggregator sites for a jRPG.