There are some challenges though. Probably the biggest one is that it's designed for a specific mail server setup: postfix + dovecot (configured for maildir) + fail2ban + php (the code is in php, because it was convenient) + mysql. I don't know yet how portable it will be.
If you'd like to try it anyway, let me know and I'll post what I've got to GitHub in the next few days.
edit: alternatively, I've been more seriously considering making the current network ban list available as an RBL. Since I already have DNS servers, it would be pretty trivial to do.