Etherpad got shut down a long while back if I remember right. The source it was based on is the preliminary test runs for what would become Google Docs. After Google Docs opened up I think the guys running the servers for Etherpad decided to shut it all down, thing was having a hard enough time dealing with traffic load at that point anyway. Well that was the online version at least, they released the source a while back and that's how titan and the others came about. 

At least that's how I remember things going down, it's been a while, might have a few gaps in my memory.