I strongly agree with Roberto that we don't want to limit this to
bboard messages. In fact, every item in the CR should be
exposed to categorization.
I wonder, though, if it's a mistake to use folders as the
categorization mechanism when the OpenACS team is actively
working on developing a CR-wide categorization mechanism
(service contract?). Why not just change the scoping on the
categorization method to allow people to create their own trees?
That way, when categorization gets enhanced and extended,
your module reaps the benefits.