Plot: Vendetta Online is a twitch-based, science fiction massively multiplayer online role-playing game developed by Guild Software for the operating systems Android, Linux, Mac OS X, iOS, and Microsoft Windows. Wikipedia
Plot: Star Conflict is a free-to-play dynamic massively multiplayer online game space action game. The gaming platform Steam describes it as an action-packed, massively multiplayer space simulation game. The core of the game is PvP spaceships battles, PvE missions and an open world. Wikipedia
Plot: Space Trader is a video game by the Canadian developer HermitWorks Entertainment, for Microsoft Windows and Mac OS X released on July 25, 2007. After the game was open-sourced in 2008, an iOS version followed in 2009. Wikipedia
Plot: Ryzom, also known as The Saga of Ryzom, is a free and open source massively multiplayer online role-playing game developed by Nevrax for Microsoft Windows, OS X, and Linux. Wikipedia