The most reliable source for a is the Internet Archive. Search for gm8_decompiler_v1.4.7z . This package typically contains a standalone Windows executable that reads extracted game.run files.
Converts .exe files from GameMaker 8.0 and 8.1 back into project files. gamemaker 8 decompiler link
Identifying why a legacy game might crash on modern hardware. A Quick Word on Ethics and Legality The most reliable source for a is the Internet Archive