Interesting, from reading their page it looks like they're planning to fork Geko at 1.3.1 (the last version that works on OS 9) and then backport changes from the more recent versions.

http://code.google.com/p/classilla/wiki/AAATheFAQ

According to the roadmap they plan to have a "no matter what" release out on the 1st of July and then a proper, stable release by the end of the year. Should be interesting to follow their progress!