Pardus

Pardus is a space-themed MMOG RPG where players interact and cooperate to build economies, fight NPCs, and bring havoc to others. It's open and highly player based world allows for players to control how the game progresses. The game is affected very little by the developers, with events such as wars, epidemics, and meteor attacks. Once you've joined, your possibilities are endless, you can cooperate to help in wars, or you can screw everything up. As it is a free game, the only thing stopping you from doing it all is signing up!