Nessiah mentioned Scirra Construct, which is an open source game maker under the GNU license. It's a newer one, so it doesn't have a big tutorial or resource base, but I rather like it more than game maker. Kind of reminiscent of rm2k, in my opinion. Anyway, game maker is fine, too.
"I would be totally embarassed to write this, even as a fakepost. it's not funny except in how you seem to think it's good. look at all the redundancies, for fuck's sake. "insipid semantics, despicable mediocrity" ugh gross gross. I want to take a shower every time I read your prose." -Steel