In many jurisdictions, reverse engineering software for personal use, interoperability (making a mod), or security research is protected under "fair use" doctrines.
Some known decompilers and tools for GameMaker Studio 2 include: gamemaker studio 2 decompiler
If you must use the VM export, utilize an obfuscator before publishing. Code obfuscators scramble script names, variable names, and asset structures into meaningless strings of characters (e.g., changing scr_player_health to _a1 ). The code will still run, but a decompiler will yield an unreadable mess. Externalize Sensitive Data The code will still run, but a decompiler
UnderAnalyzer is a library-focused approach to GameMaker reverse engineering. "Written in C#, with interfaces that map to existing structures in game data", UnderAnalyzer provides both decompilation and compilation capabilities. Its features include: Its features include: Examining how a specific mechanics
Examining how a specific mechanics system works to improve one's own programming logic.
GameBreaker aims to be "a complete suite for reverse-engineering and modifying GameMaker games compiled to bytecode for VM runners". The project is designed to be version-agnostic and game-agnostic, supporting any titles that work with UndertaleModTool and DogScepter.
However, unlike engines like Unity or Unreal, where asset extraction is relatively standardized, the GMS2 decompiler landscape is a fragmented, community-driven effort.