I would very much prefer using Guile over mit-scheme
>>1
SchemeBBS uses lots of MIT Scheme specific functions. There are many workarounds in SchemeBBS due to the limitations and age of MIT Scheme. This could be avoided by using Guile instead. However, SchemeBBS is staunchly in the MIT Scheme + SICP camp, so it is not likely to support other Scheme implementations.
>>1
If you're willing to do most of the porting work yourself, some of us will chip in https://textboard.org/prog/140#t140p33 with fixes.
Also see https://github.com/ECHibiki/Kotatsu-V for a guile chan, though it has plenty of rough edges.