Myst Online: Uru Live is a massively multiplayer online adventure game developed by Cyan Worlds. The game is the multiplayer component to the 2003 video game Uru: Ages Beyond Myst. Like Uru, Myst Online takes place in 2000's New Mexico, where an ancient civilization known as the D'ni once thrived. The D'ni had the ability to create portals to other worlds or Ages by writing descriptive books of the Age. Players uncover clues and solve puzzles together; plot developments were added via episodic content updates.
Uru's multiplayer segment was delayed and did not ship with the single-player component as planned; in February 2004 the multiplayer was scrapped entirely. Dedicated fans kept an unsupported version of the game alive through Cyan-maintained servers. Online game distributor GameTap resurrected the game as Myst Online in 2007, but this version was canceled due to a lack of subscribers despite generally positive reviews. Cyan received the rights to Myst Online from GameTap and has announced their intention to bring the game back.
In 2010, Cyan Worlds released the game free of charge, under the name MO:ULagain. It is currently hosted on Cyan-maintained servers.
Source: Wikipedia, "Myst Online: Uru Live", available under the CC-BY-SA License.