QMM (Q3 MultiMod) is a plugin manager for Quake 3 that sits between the Q3 engine and the actual game mod to allow pseudo-mods to be dynamically loaded adding new functionality to a Quake 3 Mod. Similar to MetaMod for HalfLife.
Moving to Github (https://github.com/thecybermind/qmm2)
Doom MetaMod (DMM) is a Doom3 modification that acts as a node between the engine and game mod, allowing plugins to be loaded which can change normally inaccessible game behavoir or add new functionality.