Simbiosis or Simergy was a new A-life simulation game in development by Steve Grand and released as open source on SourceForge. He describes it as "a 3D underwater environment in which you can build artificial lifeforms by plugging together ‘cells’".
August 30th, 2009 Update
Per Steve's comments on Biota Live last week, I (aka User:Barbalet) was passed the source code of Simbiosis this morning. Steve has asked me to look through it with the potential of moving it open source. Whilst I won't be able to provide the source code to anyone just yet, I am interested in hearing from people who would like to develop it as an open source project. Please let me know (tom at nobleape dot com)...
June 24th, 2010 Update
The project was released as Simergy on SourceForge as the name Simbiosis was taken.