DasForum is a PHP BulletinBoardSystem. It uses MySQL, PostgreSQL or SQLite as it's database.
It comes with Calendar, Votes, FAQ, Usergroups, Moderation System, Userranks, Modules with Blogs and Messaging-System....
It's not yet complete, but already usable.
You should rather use cvs or the nightly tarball from http://savannah.nongnu.org/cvs-backup/dasforum-sources.tar.gz than the archive from the files section.
These details are provided for information only. No information here is legal advice and should not be used as such.