Essentially, robomoderators, moderation support programs, and mail to
news gateways are all the same thing.  They take an incoming message,
from either an MTA or from a user filtering program like procmail, or
perhaps even directly from a user's MUA, perform a variety of rewrites
required to turn an RFC 822 message into an RFC 1036 message, possibly
perform a variety of checks and additional rewrites suited to the
particular application, and then hand the message off to a news
server.  News to mail gateways just do exactly the same thing in
reverse.

This is an attempt to generalize out the framework, so that people
don't have to keep writing the same code to read e-mail messages, post
messages, send e-mail messages, and do the common rewrites, and
instead can concentrate on the *interesting* parts, namely the checks
and rewrites they need for their specific application.  News::Gateway
is *not* a robomoderator or gateway in and of itself.  Rather, it's a
toolkit for *building* robomoderators and gateways that attempts to
take care of all of the nitpicking details for you and drastically
decrease the amount of code you have to write.