GNU diff utilities

http://www.gnu.org/software/diffutils/diffutils.html

Open source video codec from the BBC

http://dirac.sourceforge.net/

Graphical diff tool

http://freecode.com/projects/dirdiff/

Client for managing and downloading certificate revocation lists

http://www.gnupg.org/aegypten2

Frontend to xgamma

http://gnu.ethz.ch/linuks.mine.nu/displaycalibrator/

Distribute compilation of C(++) code acrosss machines on a network

http://distcc.org

Extremely fast library for floating-point convolution

http://cr.yp.to/djbfft.html

FTP benchmark program

http://www.kegel.com/dkftpbench/

Another hyper make utility

http://code.google.com/a/apache-extras.org/p/dmake/

Portable debug memory allocation library

http://dmalloc.com/

X11 menu application designed for the dwm window manager

https://tools.suckless.org/dmenu

Tool for dumping DMI (SMBIOS) contents in human-readable format

https://www.nongnu.org/dmidecode/

DMX extension headers

http://www.freedesktop.org/wiki/Software/xlibs

Distributed.net distributed computing project client

http://www.distributed.net/

Simple sudo alternative to run commands as another user

https://github.com/slicer69/doas/

Meta-port for the different versions of the DocBook DTD

http://www.oasis-open.org/docbook/

DocBook SGML DTD

http://www.oasis-open.org/docbook/

DocBook SGML DTD into nroff/troff -man macros converter

https://www.oasis-open.org/docbook/tools/dtm/

Generates various output formats from DocBook SGML documents

http://sources.redhat.com/docbook-tools/

DocBook XML DTD

https://www.oasis-open.org/docbook/

DocBook W3C XML Schema

https://www.oasis-open.org/docbook/xmlschema/1.0b1/

XSL DocBook stylesheets

http://docbook.sourceforge.net/projects/xsl/

Emacs lisp modules for editing DocBook documents

http://nwalsh.com/emacs/docbookide/

Dockapp with support for GNOME2 and KDE3 tray icons

http://icculus.org/openbox/2/docker/

Docker containment system

https://github.com/kvasdopil/docker

DOCSIS(tm) binary configuration file encoder/decoder

https://github.com/rlaager/docsis

Doom data files (Doom, Doom II, Hexen, Heretic and Strife)

Complete Doom-based game IWAD that is Free Software

http://freedoom.sf.net/

Improved and extended version of Doom

http://doomlegacy.sourceforge.net/

UNIX rewrite of a game originally based on "Drug Wars"

http://dopewars.sourceforge.net/

Emulator of a PC with DOS

http://dosbox.sourceforge.net/

Simple, powerful configuration-file parser

https://github.com/williamh/dotconf

Secure, fast and powerful IMAP and POP3 server

http://www.dovecot.org/

Documentation system for C, C++, and other languages

https://www.doxygen.org/

OpenGL hardware acceleration drivers for the DRI

http://dri.sourceforge.net/

DRI2 prototype headers

http://www.freedesktop.org/wiki/Software/xlibs

Blog editor for GNOME

http://drivel.sourceforge.net/

The Droid typeface family

https://www.droidfonts.com/

Database driven web content management system (CMS)

https://www.drupal.org/

Database driven web content management system (CMS)

https://www.drupal.org/

DSSSL stylesheets for the DocBook DTD by Norman Walsh

http://sourceforge.net/projects/docbook/

Silently consume flash MIME types

http://www.gsoft.com.au/~doconnor/nullflash.html

English to Thai dictionary for GNUstep

http://www.eskimo.com/~pburns/Dictionaries/

DVD burning software

http://fy.chalmers.se/~appro/linux/DVD+RW/

Backup content from DVD to hard disk

http://dvdbackup.sourceforge.net/

Utilities & library to manipulate ext2/3/4 filesystems

http://e2fsprogs.sourceforge.net/

Blkid library from e2fsprogs package

http://e2fsprogs.sourceforge.net/

UUID library from e2fsprogs package

http://e2fsprogs.sourceforge.net/

EFL DBUS connectivity library

http://docs.enlightenment.org/api/e_dbus/html/

Small RSA key management package based on openssl

https://github.com/OpenVPN/easy-rsa