From a Usenet posting: BetaBoard. This is a shareware board written in MS-BASIC; sources are readily available. It was the first; it's pretty primitive but is relatively easy to customize. I don't know too much about its abilities, but I'm certain it supports at least checksum XMODEM. --- From the author, Todd Nix: I was the author of BetaBoard - worked on the code in my dorm room at Rice University in 1984-1985 instead of going to class and earned a semester of scholastic probation for it. I ran a site using BetaBoard in both Houston and Lubbock Texas in 1984-1986 before finally shutting it down when I returned to college. It was written in MSBasic - I still have a few MSBasic handbooks on my bookshelf. I remember I got the base modem code from another BBS software, but I did a lot of work enhancing the menus and customization options. I accepted shareware payments - probably only received 20-30 payments - but there were definitely other folks hosting sites using it. I don't believe I have a copy of the code anymore, but there might be a copy hidden somewhere in the attic.