OpenGL extension to GTK+

http://gtkglext.sourceforge.net/

GTK client for posting JustJournal entries

http://www.justjournal.com/

C++ wrapper for Gtk+

https://www.gtkmm.org/

C++ wrapper for Gtk+3

http://gtkmm.sourceforge.net/

Measure your system's GTK+ performance

http://gtkperf.sourceforge.net

Widget that adds syntax highlighting to GtkTextView

Text widget that adds syntax highlighting to the GtkTextView widget

https://wiki.gnome.org/Projects/GtkSourceView/

Text widget that adds syntax highlighting to the GtkTextView widget

https://wiki.gnome.org/Projects/GtkSourceView

A GTK+ 2 spell checking component

http://gtkspell.sourceforge.net/

GTK+ 3 spell checking component

http://gtkspell.sourceforge.net/

Interactive typing tutor

http://www.gnu.org/software/gtypist/

Unicode/ISO10646 character map and font viewer

https://wiki.gnome.org/Gucharmap

GNU Ubiquitous Intelligent Language for Extension

http://www.gnu.org/software/guile/

GNU Ubiquitous Intelligent Language for Extension

https://www.gnu.org/software/guile/

Pure-C HTML5 parser

https://github.com/google/gumbo-parser

GutenPrint Printer Driver

http://gimp-print.sourceforge.net/

PostScript and PDF previewer

http://www.gnu.org/software/gv/

GNOME virtual file system

https://www.gnome.org/

GNUstep workspace manager

http://www.gnustep.it/enrico/gworkspace/

GWMetadata for GNUstep workspace manager

http://www.gnustep.it/enrico/gworkspace/

Compression utility designed to be a replacement for compress

http://www.gnu.org/software/gzip/

gzip recovery toolkit

https://www.urbanophile.com/arenn/hacking/gzrt/

Typeface designed for source code

https://sourcefoundry.org/hack/

Apache Map/Reduce framework

http://hadoop.apache.org/

Hardware Abstraction Layer for simplifying device access

http://www.freedesktop.org/Software/hal

Additional FDI files to further classify HAL devices

http://www.freedesktop.org/Software/hal

Library of matchers for building test expressions

http://hamcrest.org/

CJK Mincho-typeface developed by Hanazono University

http://fonts.jp/hanazono/

OpenType text shaping engine

https://harfbuzz.github.io/

OpenType text shaping engine

https://harfbuzz.github.io/

OpenType text shaping engine

https://harfbuzz.github.io/

Anti-spam / denial of service counter-measure tool

http://www.hashcash.org/

Hierarchical Data Format library (from NCSA)

https://www.hdfgroup.org/

Portable and enhanced troff, nroff, and related utilities

https://n-t-roff.github.io/heirloom/doctools.html

Automatically generating simple manual pages from program output

https://www.gnu.org/software/help2man/

Online help viewer for GNUstep programs

http://www.roard.com/helpviewer/

Monospaced font for programmers by a programmer

https://pcaro.es/p/hermit/

Tiny program that sends some load to a web application

https://github.com/rakyll/hey

High-color icon theme shell from the FreeDesktop project

http://www.freedesktop.org/Standards/icon-theme-spec

Customizable syntax highlighter

http://www.andre-simon.de/

Framework needed by Project Manager

http://home.gna.org/pmanager/

Performance-portable, length-agnostic SIMD with runtime dispatch

https://github.com/google/highway

Minimalistic C client library for the Redis database

https://github.com/redis/hiredis

Hitori

https://wiki.gnome.org/Apps/Hitori

Split files into encrypted fragments

https://github.com/jesseduffield/horcrux

IEEE 802.11 AP, IEEE 802.1X/WPA/WPA2/EAP/RADIUS Authenticator

https://w1.fi/hostapd/

Small utility which displays the system activity in a very special way

http://dindinx.net/hotbabe/

Network auditing tool

http://www.hping.org/

Hebrew spellchecker and morphology engine

http://hspell.ivrix.org.il

All W3C published SGML DTDs for HTML