nBB2 - the classic forum engine now in Java
nBB2 is the Java counterpart of the phpBB project version 2.0.22.
nBB2 is open-source under the GPL license, same as phpBB. It currently provides almost all of the original functionality, with comparable performance.
Give it a try!
See nBB2 in action as the official Numiton forum.
Go here if you want to obtain and install the binary distribution.
If you are interested in the source code or want to contribute, take a look at the Development section.