From Alex Wetmore's Site:
Yabbs was conceived during my winter break in 1991 (my freshman year of college at Carnegie Mellon University). I wrote it because I was bored and because I wanted to run a BBS on the internet, but didn't know of any good software to do that at the time.
I started out being written under MS-DOS as a console program (I was going to add networking code later). My intentions were to get a system up that allowed for simple sending and receiving of public messages (no email, no talk, no g-files). It was only going to allow one user on a time (since MS-DOS doesn't have any good multitasking abilities). My plan was to merge in some MS-DOS networking code that I had hacked together for another earlier project (wall, which allowed users to telnet to a MS-DOS machine running PC/TCP and scribble one-liners). Once this was done I figured I'd have something online and hack it out from there.
I never did get the MS-DOS networking stuff merged in. When I got back to school I decided that Unix was the way to go with this stuff (MS-DOS is really braindead). I didn't personally have a machine that I could use to develop it, but a friend of a friend offered me an account on his NeXT workstation. I hacked in some unix networking code and got it running on that.