I still visit some web forums that has been online since the 90's. At least two still use the same ancient software that they have used since ~1995. One of those is shut down a few hours every night (US time) for "database maintenance". I find that more adorable than annoying.

Used to hate web-forums. Usability is so bad compared to USENET. But now they are goldmines of probably unique content, and far better than Discord or Facebook Groups.

xenforo that spacebattles is based on seems pretty good, but it appears to be a package deal with hosting (which I suppose funds its development).

https://xenforo.com/purchase/

edit: found a license only page:

https://xenforo.com/purchase/#licenses

but it seems you only get 1 year of updates for the $160, and then you have to pay the fee again, so even if its lifetime use you will probably want to continue to pay for security or whatever else updates.

https://offtopic.com/ is still going and I believe it started in 2000?