Thanks for advice. Yeah, I saw info about weird patches in SchemeBBS README, so I decided not to use it for my textboard. However, this IB engine with Guile looks neat: https://github.com/ECHibiki/Kotatsu-V/
Aside Guile, I see here's a bunch of interpretators/compilers available: https://wiki.archlinux.org/title/Scheme
Can you tell us anything good or bad about them?