Pipo-BBS allows you to install a BBS server and clients. You can chat via a nice interface with an unlimited number of people (as with IRC). This software is in a pre-release state; it is still very alpha, and can be difficult to even compile. It works under linux, MkLinux, SGI, HP-UX, and Solaris. The only interface for this BBS is telnet for the moment; an interface using GTK has been started. It has been translated into French, English, Spanish and German.
DBOX is a free communication package for ISPs. It supports a large number of message formats such as RFC/UUCP, ZConnect, Janus/Janus2, Alphabox, and GSbox. It is designed for large installations and includes a WWW package with an email/HTML gateway, an HTML online shop, support for POP3/IMAP4, and personal homepages with HTTP/FTP upload.
aGNeS is a solid BBS system from Vestris Inc. aGNeS allows threaded discussions, article searching, archiving, thread expanding and collapsing, etc. It allows to setup as many web boards as desired with totally different layout , using one CGI. The look and feel of your forum can be just whatever you like using template pages. aGNeS is web-administrable. There are tons of features and options.
falmsg is a small utility that was designed for other sysops that are running the Falken BBS for Linux. It updates the .msg files that come with the distribution of Falken BBS, along with a few other small features. You can backup Falken BBS, restore Falken BBS, and erase the backup copy that is created using this program. falmsg is merely a front-end to a couple of other programs such as lynx, tar, telnet, and Falken BBS.