It's been a long time since I used it, and I've read that there was a messed version change since then. So take it with a pinch of salt. Drupal had a very nice

It's been a long time since I used it, and I've read that there was a messed version change since then. So take it with a pinch of salt. Drupal had a very nice hybrid of forum and wiki, it was called "book" IIRC. It was possible to organize the pages in a hierarchy and at the same time it provided discussion in every node. Being modular and open source, you could add the import thing. I've been working in importing stuff for a while so maybe I see it easier than it is. The community features were very good, with a nice permissions system.