Hi, Tom - just got back from some travel and saw your message. Development has been going strong on the Knitter project, which uses Cartagen to do web-based orthorectification of aerial imagery. Knitter is part of the Cartagen codebase, and available at
http://cartagen.org/maps
However it's diverged so far from the Cartagen framework that it really belongs in its own repo. Cartagen itself has had minimal development although i've been adding small utility functions and catching bugs from time to time. For example i revised the keypress event system significantly and have restructured how new tools are added to make it more extensible. I believe some folks on this list have made improvements too but I haven't been able to pull them back into trunk yet.
My plan in the next month or so once i have a moment is to move Knitter to its own repo, then make an alternate branch for the Cartagen Server software, leaving only the client side system in the main trunk repository. That will vastly simplify things for the majority of users who simply want some client side maps without running a big Ruby server. I'd like to fork off some of the conversion utilities too so that there's a standard set of scripts to convert to JSON from XML or other sources, but I don't see that happening soon.
If I had a clearer idea of what people are trying to do with Cartagen it'd be easier to prioritize things (and to motivate and make time). However the main use right now is as part of the Knitter system which I'm spending a good bit of time on, and that doesn't use vector data that much.
Thanks for your interest!
Jeff