GNU version of the traditional tape archiver

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

Code documentation system, originally for GTK+

https://www.gtk.org/

Theme engine for the GTK+-2.0 toolkit

https://www.gtk.org/

Murrine GTK+ 2.x cairo based engine

http://www.cimitan.com/murrine

Extensions on top of GTK-sharp

http://gitorious.org/gtk-sharp-beans

GTK+ and GNOME interfaces for the .NET runtime

http://www.mono-project.com/Gtk

GTK+ and GNOME interfaces for the .NET runtime

http://www.mono-project.com/Gtk

Gtk-update-icon-cache utility from the Gtk+ toolkit

https://www.gtk.org/

VNC viewer widget for GTK+

http://live.gnome.org/gtk-vnc

Xfce gtk theme engine

http://www.xfce.org/

Gimp Toolkit for X11 GUI (previous stable version)

https://www.gtk.org/

Gimp Toolkit for X11 GUI (current stable version)

https://www.gtk.org/

OpenGL extension to GTK+

http://gtkglext.sourceforge.net/

Lightweight HTML rendering/printing/editing engine

http://www.ximian.com/

GTK client for posting JustJournal entries

http://www.justjournal.com/

C++ wrapper for Gtk+, Pango, Atk, and Glib

http://gtkmm.sourceforge.net/

C++ wrapper for Gtk+

https://www.gtkmm.org/

C++ wrapper for Gtk+3

http://gtkmm.sourceforge.net/

GTK+ UI debugging tool

http://chipx86.github.com/gtkparasite/

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/

Programming reference for x11-toolkits/gtksourceview3

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/

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/

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/