Generates groff and HTML from linuxdoc and docbook SGML documents

SGML parser

GLSL/HLSL to SPIR-V shader compiler

https://github.com/google/shaderc

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/

Collection of shareware ATM fonts from the CICA archives

Pack, send, and unpack shell archives; synchronize via e-mail

https://www.gnu.org/s/sharutils/

Generic script compiler

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

Benchmark utility for POSIX shell comparison

https://github.com/shellspec/shellbench

Font dumper for the X font server

https://www.x.org/

xUnit based unit testing for Unix shell scripts

https://github.com/kward/shunit2/

Text based Hotline Communications client for Unix

http://synhxd.sourceforge.net/

HTTP regression testing and benchmarking utility

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

MacOS High Sierra like theme for GTK 3, GTK 2 and Gnome-Shell etc

https://github.com/vinceliuice/Sierra-gtk-theme

GPG/PGP Keyring Graph Generator

http://www.chaosreigns.com/code/sig2dot/

Sigar system information API

https://support.hyperic.com/display/SIGAR/Home

Command-line and D-Bus interface for Signal and libsignal-service-java

https://github.com/AsamK/signal-cli

FTS5 extension for signal_tokenizer

https://github.com/signalapp/Signal-FTS5-Extension

Create and verify cryptographic signatures

https://github.com/leahneukirchen/outils/

Sigrok firmware

https://www.sigrok.org/wiki/Firmware

Cypress FX2 firmware for hardware logic analyzers

https://www.sigrok.org/wiki/Fx2lafw

Sigrok firmware extraction utilities

https://www.sigrok.org/wiki/Firmware

Secure Internet Live Conferencing (SILC) network toolkit

http://www.silcnet.org/

Font engine for complex non-Roman writing systems

http://silgraphite.sourceforge.net/

Simple MTP fuse filesystem driver

https://github.com/phatina/simple-mtpfs

simple calendar and agenda application

http://wiki.gnustep.org/index.php/SimpleAgenda.app

C++ library providing a simple API to INI-style configuration files

https://github.com/brofield/simpleini

Extremely simple IRC client

http://www.suckless.org/programs/sic.html

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

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

Maintains remote websites, uses FTP or WebDAV to sync up w/ local copy

https://www.manyfish.co.uk/sitecopy/

General purpose C libraries used by skarnet.org software

https://www.skarnet.org/software/skalibs/

Slack client for your terminal

https://github.com/erroneousboat/slack-term

Tool for checking, and diagnosing DNS zones

Simple facade or abstraction for various logging frameworks

https://www.slf4j.org/

Graphical login manager for X11, derived from Login.app

https://sourceforge.net/projects/slim.berlios/

Theme pack for SLiM login app

https://contents.meetbsd.ir/apps/opensource/slim/

Superior Lisp Interaction Mode for Emacs

https://common-lisp.net/project/slime/

Low-bandwidth, yet greedy and poisonous HTTP client

http://ha.ckers.org/slowloris/

SLang-based newsreader

https://slrn.sourceforge.net/

Multi-layered IRC library

http://smartirc4net.meebey.net/jaws/

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

https://www.smartmontools.org

Samba-LDAP management and support tools

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

Free MPEG1 video player library with sound support

https://www.lokigames.com/development/smpeg.php3

Session Manager Proxy

Fast compressor/decompressor library

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

Fast compressor/decompressor library

https://github.com/xerial/snappy-java

Small audio and MIDI framework from the OpenBSD project

http://www.sndio.org/

Lightweight network intrusion detection system

https://www.snort.org/

Snowball stemmer library for C

https://snowballstem.org/

Vendor and platform neutral SDR support library

https://github.com/pothosware/SoapySDR