RBBS-PC (acronym for Remote Bulletin Board System for the Personal Computer) was a freeware, open-source BBS software program. It was written entirely in BASIC by a large team of people, starting with Russell Lane and then later enhanced by Tom Mack, Ken Goosens and others.
It supported messaging conferences, questionnaires, doors (through the DORINFO1.DEF dropfile), file sharing and much more.