WikiBattle - 1v1 race who first reaches a randomly selected article.
Hordes - Free to play 3D Multiplayer Browsergame in Open Beta.
OneLife - Multiplayer survival game of parenting and civilization building.
OpenMW - Open-source open-world RPG game engine that supports playing Morrowind.
OpenDiablo2 - Open source re-implementation of Diablo 2.
Pioneer - Game of lonely space adventure.
openage - Free (as in freedom) open source clone of the Age of Empires II engine.
AIDungeon2 - Infinite adventures await.
Julius - Open source re-implementation of Caesar III.