Myst Online. The fantasy MMORPG began its checkered life as the multiplayer component of 2003's Uru: Ages Beyond Mist before being scrapped and subsequently revived by GameTap in 2007.
Cyan Worlds then acquired the title and released it as a free-to-play MMO, a strange move considering that the company also open-sourced Myst Online assets in 2008 but continued to support a commercial-grade centralized shard.
This morning, Rock, Paper Shotgun tipped us to the fact that Cyan is once again fanning the flames of open source by announcing that the game's MOULA client engine and associated development tools (as well as a MOULA server replacement called MOSS) will be made available and hosted on OpenUru.org. "The goal of the open source CyanWorlds.com Engine and the MOSS server is to provide a playground where new writers can learn their craft, and new maintainers can inspect it, and new cartographers can map it. The Cyan Worlds MOULA servers will continue to provide a (relatively) safe environment for the D'ni faithful to mingle and share," explains Cyan's Rand Miller.