If the modern Rust-based tool doesn't meet your needs, there are legacy alternatives still floating around the web:
A interesting topic!
The GameMaker 8 decompiler is a tool that aims to decompile GameMaker 8 game files (with the .gmk or .gmx extension) into a human-readable format. This can be useful for: gamemaker 8 decompiler link
Fixed conversion for better performance on new GPUs. If the modern Rust-based tool doesn't meet your
This report details the primary tools and methods available for decompiling GameMaker 8 (GM8) executables back into their original project formats. gamemaker 8 decompiler link