Cross-platform multimedia development API

https://www.libsdl.org/

"Simplified" DocBook XML DTD

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

Extensive german HTML reference

http://www.selfhtml.org/

Serf HTTP client library

https://serf.apache.org/

Manage utmp/wtmp entries for non-init X clients

Set the keyboard using the X Keyboard Extension

https://www.freedesktop.org/Software/xorg

Set of utilities that send SCSI commands to devices

http://sg.danny.cz/sg/sg3_utils.html

Generates groff and HTML from linuxdoc and docbook SGML documents

Interoperability between desktops and collaborative environments

http://oscaf.sourceforge.net

MIME types database from the freedesktop.org project

https://www.freedesktop.org/wiki/Software/shared-mime-info/

Generic script compiler

https://github.com/neurobin/shc/

Font dumper for the X font server

https://www.x.org/

HTTP regression testing and benchmarking utility

https://www.joedog.org/JoeDog/Sieg

Secure Internet Live Conferencing (SILC) network toolkit

http://www.silcnet.org/

Small (150k), fast, perl-based IRC client

http://www.iagora.com/~espel/sirc.html

SixXS IPv6 TIC+ tunnel broker heartbeat client

http://www.sixxs.net/tools/aiccu/

SLang-based newsreader

https://slrn.sourceforge.net/

SIP scanner and identifier

http://www.wormulon.net/

S.M.A.R.T. disk monitoring tools

https://www.smartmontools.org

Samba-LDAP management and support tools

https://gna.org/projects/smbldap-tools/

Session Manager Proxy

Fast compressor/decompressor library

https://google.github.io/snappy/

Flow-based network traffic analyzer and exporter

http://www.mindrot.org/softflowd.html

Highly efficient mail filter for identifying spam

https://spamassassin.apache.org/

Traps spammers with a very slow smtp-login and return 4xx error

https://freebsdspamd.sourceforge.net/

Spawns fastcgi applications

http://redmine.lighttpd.net/projects/spawn-fcgi

open-source patent-free voice codec

http://www.speex.org/

Audio compression format designed for speech

http://www.speex.org/

Sphinx Full-Text Search Engine

https://sphinxsearch.com/

Standalone JavaScript based from Mozilla 17-esr

http://www.mozilla.org/js/spidermonkey/

Standalone JavaScript (1.8.5) interpreter from Mozilla

http://www.mozilla.org/js/spidermonkey/

Tool for statically checking sourcecode for security vulnerabilities

https://www.splint.org/

SQL database engine in a C library (TCL flavor)

https://www.sqlite.org/

HTTP Caching Proxy

http://www.squid-cache.org/

Webmail system which accesses mail over IMAP

https://www.squirrelmail.org/

Protect hosts from brute-force attacks against SSH and other services

https://www.sshguard.net/

Protect hosts from brute force attacks against ssh and other services using ipfilter

http://sshguard.sourceforge.net

Protect hosts from brute force attacks against ssh using ipfw

http://sshguard.sourceforge.net

Protect hosts from brute force attacks against ssh using pf

http://sshguard.sourceforge.net

State Threads Library for Internet Applications

http://state-threads.sourceforge.net/

Library that supports startup notification spec from freedesktop.org

https://www.freedesktop.org/wiki/Software/startup-notification/

Advanced IP/IPv6 subnet calculation and discovery

http://www.seccuris.com

Version control system

http://subversion.apache.org/

Allow others to run commands as root

https://www.sudo.ws/

Low level console graphics library

http://www.svgalib.org/

Summarizes and manages differences between local files and Subversion

http://www.incava.org/projects/svndelta/

Simplified Wrapper and Interface Generator

http://www.swig.org/

Generate wrappers for calling C/C++ code from other languages

http://www.swig.org/

Mouse and keyboard sharing utility

https://symless.com/synergy

Helps to install application configuration files

https://www.Courier-MTA.org/sysconftool