Ryzom

Ryzom is a free-to-play fantasy/sci-fi sandbox that puts critical decisions in the hands of players and constantly evolves based on their actions. With updated graphics for its Steam launch, Ryzom is waiting to be discovered by a new generation of gamers looking for a truly immersive experience.

There are no classes in Ryzom, so you're free to choose whatever path you like, and advance the skills that are important to you. The game has a ton of different activities, including interactive events with NPCs that offer plenty of possibilities for role-playing interactions. Monsters invade cities, and players can challenge each other in PvP, but only if all players consent to it -- no anarchic gankbox here!

Rare in the MMORPG landscape, Ryzom is completely open-source, meaning that the community can easily contribute functionality to the core game. Its open development process has kept it going for over a decade and won it thousands of devoted fans from around the globe.