"Their version" is completely different from the mac game maker... it's not even really a programming tool, you just select actions that occur to objects when conditions are met... although I think it has it's own tiny scripting language. The problem is that it is ridiculously easy to use, so it's really popular, and you get a ton of crappy games. It is advanced enough to make wolfenstein 3d style raycasters, and relatively advanced RTS games. Basically, from the point of view of the average person it's better than our GM in every way.
We should post a banner on the homepage that differentiates the two programs to avoid confusion/ lawsuits.