"Game decompilation is the process of reverse-engineering a compiled game executable to recreate its original, human-readable source code (typically in C or C++) without using the developer's original files. "- Brave ai definition
In laymen's terms reversed engineered pc ports of video games.
for example: The recently released Zelda:Twilight Princess Decomp project- Dusk
Decomps are in a weird legal spot as you aren't downloading the game but rather downloading something that modifies it from reverse engineered work. Most companies make a stink about it for physical items but, I haven't seen any video game devs take action on it, yet. No doubt Nintendo will be the first, especially if it's a major Pokemon decomp that eclipses the original game the decomp is based on.
Here's some reimplementation projects from reverse engineering of PC games I've come across:
Arcanum CE - The reverse engineering is complete and people have played through the game, but I'd expect it to be buggy as was the original game. The same author has also reimplementations for Fallout 1 and 2 that are mature.
Dethrace (Caramageddon) - Seems close to completion as they report 95.55% accuracy.
Heretic2R - This is fairly new, but apparently feature complete. The readme mentions framerates above 60 FPS haven't been tested.
OpenJKDF2 (Jedi Knight: Dark Forces II) - Seems fairly mature. Allows playing at unlocked framerates, whereas the original game shits the bed at framerates above 30 FPS. Also supports the Mysteries of the Sith expansion, but this is marked as beta.
