Client
Avaraline Client List, BBSzilla, DefBot, Fidelio, Frogblast, GHX, GtkHX, Heidrun, HotlineX, HotPants
Server
Avaraline VertiServer, Codebox Tracker, Hotline Connect Admin Tool, Hotline NetStrangler, HotlineX, hotwired, HSX, OpenSprings Project, SilverWing Server, Soja
CAPS
A hotline client (RedCap) and server (BlueCap) package designed to be an improvement over the official client and server.
Free HL Iconlib
A free and opensource Java library for extracting icons and GIF-images from the hotline.dat file of the Hotline software provided by Hotsprings, Inc.
Net-Hotline
A set of modules for utilizing the Hotline protocol in a Perl environment.