When you are looking at each server there is information at the bottom such as engage distane and dismember threshold. These are just changes to the game rules. However, the mod is also listed at the bottom if you look carefully. Kickbox, judo, wushu and tae kwon are all classic mod, but then there are mods used in multiplayer too like joust.
Edit: Pirate said aikido isnt a mod, when it is, its a variation of sambo