Software

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.
http://www.markusstengel.de/hliclib.html

GLoarbLine Suite
Open source Hotline client and server applications for various operating systems derived from OpenLine which was one of the first free Hotline clones.
http://gloarbline.free.fr/

HotlineX
Free set of software using the Hotline protocols, providing Hotline application suites that can run on GNU/Linux, OS X and Unix. Provides release information for the base HXD products as well as mHXD.
http://hotlinex.sourceforge.net/

Net-Hotline
A set of modules for utilizing the Hotline protocol in a Perl environment.
http://search.cpan.org/dist/Net-Hotline/

SourceForge.net: PhareRouge
Open source, GNU/Linux-compatible version of the now unavailable Red Light Variety Alpha software, a Hotline protocol client and server with English and Japanese language support.
http://pharerouge.sourceforge.net/

SourceForge.net: PhareRouge GL
An improved version with additional features making it compatible with GLoarbLine server and 1.9x servers.
http://sourceforge.net/projects/pharerougegl/