Lot of problems with Mac/Linux exporter in GameMaker. You should try the demo and use some of the tricks to run win apps on Mac, like VirtualSO , WineHQ or similar, due is a small app should work.
I hope a Mac version will eventually be planned at some point, similar to both PixaTool & Pixel FX Designer, which was mainly the reason why I bought both. A lot of Sprite-Designing software out there tends to be Windows-Only, I find. And this kind of limits my options as a Mac User.
I can use something like WineHQ for the time being though, I suppose.
