From the included Read Me: GM Carbonizer takes any game compiled with
GameMaker v1.5 and up and converts it to a Carbonized GameMaker v3.7
game. This allows you to play old GameMaker games natively on Mac OS
X. You can also use it to convert an old 68K game so it runs more
quickly on Mac OS 8.6 and up with CarbonLib.

Example on Game Maker games here:
[The Anaphobian Planet][1] which could be converted to run under OSX.
Note: not tested this one.

Compatibility
Architecture: PPC PPC (Carbonized)

Carbonizer's System Requirements:
GM Carbonizer requires Mac OS 8.6 and up with CarbonLib v1.1 and up,
or Mac OS 10.1.5 and up.
Carbonized Game's System Requirements:
Mac OS 8.6 and up with CarbonLib v1.4 and up, or Mac OS 10.1 and up.

  [1]: http://macintoshgarden.org/games/the-anaphobian-planet