I would love something that is close to phpBB but slightly more modern. Like, phpBB but with federation support and a clean API would be great. But most modern forum-like software is Reddit clones.
How I miss my script kiddie days of being 15, downloading "nulled" versions of vBulletin off of Limewire and throwing them up on pocket money paid cPanel web hosting account waiting for it to upload on my parents 56K.