Jon, I believe
Gustaf
was trying out
Naviserver
with OpenACS last year sometime. If I remember right, his conclustion
at the time was that it looked promising, but the code was changing
too fast for him to want to try and keep up with it, easier to wait
and re-evaluate once Zoran, Stephen, and Vlad slowed down in their
changes. Perhaps that's happened now, I don't know - I'm sure the
three Naviserver guys would be happy to fill you in, though.