Not sure what a BBS is? This video provides a good introduction.
Synchronet BBS Software is a free software package that can turn your personal computer (or embedded system) into your own custom online service supporting multiple simultaneous users with hierarchical message and file areas, multi-user chat, and the ever-popular BBS door games.
Synchronet development began as a personal hobby in 1990 for single-tasking MS-DOS compatible computers and Hayes compatible modems. The program was sold commercially from 1992 to 1996 after which time it was released (with source code) for both the 16-bit DOS and 32-bit OS/2 platforms to the public domain and development by the author was ceased.
In November of 1999, the author found a renewed interest in further developing Synchronet, specifically for the Internet community, embracing and integrating standard Internet protocols such as Telnet, FTP, SMTP, POP3, IRC, NNTP, and HTTP. Synchronet has since been substantially redesigned as an Internet BBS package for Windows and Unix platforms and is an Open Source project under continuous development.