This forum is closed to new posts due to low activity and a deluge of spam. It is kept online as a static historical record. If you want to read about or discuss esoteric programming languages, the Esolang wiki is the place to go. An archive of the forum is available.
I also would prefer phpBB to this software. Mainly it is the option to have sub-forums that I miss. That is only important if we get a significant amount of traffic, of course.
Btw, phpBB doesn't require users to register (though you may require it if you want to).