Gnuserv allows you to attach to an already running Emacs. This allows external programs to make use of Emacs' editing capabilities. It is similar to GNU Emacs' emacsclient, but has a slightly different feature set.

You do not need this package if you use XEmacs; it already includes gnuserv and gnuclient. If you want to use gnuserv with both GNU Emacs and XEmacs, you will only be able to use the alternative /usr/bin/gnuclient with one flavor of emacs; you will have to use either gnuclient.xemacs or gnuclient.emacs for the other flavor.