Hello again Jason.
Now this i can be more a help with. Enigma is free and open source, therefore requires no lisensing. GameMaker and gameMaker:Studio from
yoyogames.com however is commerial to unlock all their features. While you can decompile legacy non-studio branded gamemaker exes thru decompilation, and there are rumors of a stidio decompiler in the works i see at random places, which that one may be just urban legend - decompilation breaks the YYG EULA and could kill your game maker softare keys, it would also allow you to steal other ppls work that could then modify to your liking, all of which very bad idead that could get you in a heap of legal issues, not worth risking, aside from the morality aspect of things.
Though what enigma does isnt decompile exes, what enigma does is load game maker and game maker studio project files, and can compile them into native platforms using our own technology (well the enigma devs technoligy as im not a contributor of the engine just yet). The formats it loads a gm binary blobs spit out by game maker for project and game settings assets and data (gmd, gmk, gm81, etc) and gm studio project folders known as gmx, written in xml directories and all the assets of the project unencrypted. enigma also has its own independant format should you not care for total GM or GMS accessability, the egm format exclusive to enigma.
Hope any of this makes sense. My head is jumbled right now and should turn in for the night, its 2:55 AM in virginia beach.
Samuel