I was using a private SVN for ActiveWriter and thanks to Hammet, the source is now available through Castle Contrib Repository.
Having source on an open repository is great. AW now has it's own Ohloh page :)

• Codebase: 27,938 LOC (Most of them generated by DSL Tools, actually:)
  
• Effort (est.): 7 Person Years
• Project Cost: $362,806

I feel good! :)