If you have specific needs not handled in the packages described here, you
may want to modify an available package's source code.  You may even want to
write your own MLM, in which case we'll add an entry to this list :-).
Almanac, BMW, Majordomo, MReply, SmartList, and TULP come with source that's
free to modify. ListProc 6.0c comes with source, but there are restrictions
on what you can modify, AND you're not allowed to distribute your changes --
this means that, except for bug fixes released by its author, the free
version of ListProc will develop no further.  CREN ListProc, LISTSERV,
Mailbase, Mercury MAISER, MX, and Smof come as binaries only, although
ListProc, LISTSERV, and Mailbase each include strategic hooks for shell
scripts, allowing you to modify the system's behavior.  Of the systems for
which you get source code, Almanac, ListProc 6.0c, MReply, and TULP are
written in C (with some shell scripts in ListProc and one optional Perl
script in TULP), BMW and Majordomo are written in Perl (one C routine in
Majordomo), and SmartList is written in a mixture of C, shell scripts, and
Procmail's rule-processing language, and IDG is written in the Korn shell.