ROM Hack of Crystal
This is the current Pokémon Orange beta release. The assets all have an 8-character "commit hash" at the end to identify the exact code they're built from.
The .gbc assets are ROMs. If you just want to play the game, download one (regular or -pss) and load it in BGB, mGBA, Gambatte, or another accurate Game Boy Color emulator. (Do not use VBA or VBA-M.)
The .sym assets are "symbol files". They're useful for debugging, or for discovering cheat codes, although cheats are not officially supported and may cause bugs or crashes. (Do not ask the developers for cheat codes.)
The orangedebug assets are ROMs and symbol files with extra features to help debug the game. Do not download these to just play with; use them to help the developers diagnose and fix bugs, or create new features.