Fofou is officially obsolete and unmaintaned as of April 2017.

For 9 years this simple forum software served me well to host discussions for SumatraPDF.

Unfortunately in April 2017 spam became a problem and I had to spend too much time deleting it.

Was it because my simplistic (but effective for 9 years) anti-spam check was cracked? Was it because human spammers paid cents per spam post took advantage of the fact that the forum didn't require registration?

I don't know but the reality is that those days to fight spam you need sophisticated technology and scale to detect spam across many forums.

I moved my forum to a hosted solution http://www.sumatrapdfreader.org/forum.html.

There's also https://www.discourse.org/ (expensive hosted option but also open-source so can be self-hosted for $20 on https://www.digitalocean.com).