Sarien is an AGI interpreter that was originally called Yggdrasil, but was renamed to avoid confusion with the Linux distribution. Sarien was originally created by Stuart George in 1999.
Sarien was an open source adventure game interpreter distributed under the GNU GPL. Since the license was compatible, and both teams felt integration into the ScummVM codebase would help the Sarien project, the Sarien codebase was used to create the AGI engine in ScummVM in 2006 (with permission). After the completion of the ScummVM engine, the Sarien project officially became part of ScummVM so as to not duplicate coding efforts.