I'm surprised that it's been two decades! Development began in 1996 as an attempt to graft an extensible architecture onto MacClade (which is now 37 years old!). That failed (historical constraints), so we began anew from nothing.

It was a big effort. In 2003 it had >150,000 lines of code (not including "{" etc), >95% by David and me. Now it has >300,000 lines, >80% by us. Days must have been longer in the past. How can 2 people keep all that in their heads at once? Can't. Modular architecture was key.