GDC organizers! They're still using the term postmortem for games that are very much alive. In this case it's Meridian 59, and former lead designer Damion Schubert will take the stage at GDC Online 2012 for a special Classic Game Postmortem lecture focused on the 1996 title.
A GDC press release says that Meridian 59 was the first MMO to charge a monthly fee and use 3-D graphics and that it "began an era that set the stage for the MMORPG genre as we know it." Schubert went on to work on titles including Shadowbane, The Sims Online, and Star Wars: The Old Republic.
[Source: GDC press release]
[Update: Reader Scotty also tipped us off to the fact that M59 is slated to go open source.]