You'd have to talk to them about that. I've arranged a license outside of that, and I think that option would be open to everyone - I guess it doesn't hurt that I've contributed a bunch of code now.
However, you could also argue that the only code of XMLVM's that you distribute is the objc compatibility library, and hence the only code you'd have to make public is anything bound to that - which would be the generated objc from your game. In all honesty, you're welcome to that
It'd be remarkbly unlikely anyone would be able to do anything with it, let alone distribute it (since Apple would stop them as it'd be a duplicate game).
GPL doesn't stop you going commercial, it just means you have to release your source, in the circumstance thats not such a BIG DEAL (tm).