I've just imported forums into the OpenACS CVS tree (development branch). This version will *only* install on Oracle right now. Note also that the UI is very hackish and NOT MEANT to be final in any way. I've been focusing on core functionality and concise, simple page flow. I was not able to reuse as much of Gilbert's bboard as I wanted, but some concepts did make it in.
In order to get forums working, you'll need to install notifications and acs-mail-lite, too. I've just tested the install on Oracle and you should be able to install acs-mail-lite, notifications, and forums. You'll need to instantiate both notifications and forums to get forums working (at least if you want to do notifications).
All notifications are instantaneous right now.
I am always open to criticism about my code, etc.. so bring it on! Just do so with the understanding that I don't like to overdesign before I code. So you'll see some missing chunks that are going to appear over time, and some total hacks that are designated as such with a clear intention on my part to fix them.
Finally: I'm going to be hacking on this hard for the next few days. If you want to help, that's great, but if you start porting to PG slowly (for example), expect it not to matter in 3 days... However, if you have many hours to dedicate to this over the next couple of days, I'm happy to collaborate (UI for example?).