Round Robin Database Tools

http://www.rrdtool.org/

Fast spam filtering system

https://rspamd.com/

Restricted Secure SHell only for sftp or/and scp

http://www.pizzashack.org/rssh/index.shtml

Network file distribution/synchronization utility

http://rsync.samba.org/

RTMP streams download utility

http://rtmpdump.mplayerhq.hu/

BitTorrent Client written in C++

https://github.com/rakshasa/rtorrent

Ruby interface to Oracle Berkeley DB revision 2 or later

https://github.com/knu/ruby-bdb

Binary data dumper module for Ruby

http://www.geocities.co.jp/SiliconValley-Oakland/2986/

Package management framework for the Ruby language

https://rubygems.org/

Object-oriented interpreted scripting language

https://www.ruby-lang.org/en/

Object-oriented interpreted scripting language

https://www.ruby-lang.org/en/

Fast, open source text processor and publishing toolchain

https://asciidoctor.org/

Fast, Enjoyable HTML Parser for Ruby

https://github.com/hpricot/hpricot

Framework-agnostic way to render logic-free views

https://github.com/mustache/mustache

Fast Markdown converter for ruby based on discount

https://dafoster.net/projects/rdiscount/

RDoc produces HTML and command-line documentation for Ruby projects

https://ruby.github.io/rdoc/

Builds manuals

https://rtomayko.github.io/ronn/

Restricted User SHell, providing limited remote access to resources

https://puszcza.gnu.org.ua/software/rush/

Language with a focus on memory safety and concurrency (FreeBSD version)

https://www.rust-lang.org/

Clone of the terminal emulator rxvt modified to support Unicode

http://software.schmorp.de/pkg/rxvt-unicode.html

Subset of a well-known texture compression scheme

https://github.com/divVerent/s2tc/wiki

nsupdate utility with the GSS-TSIG support

https://www.isc.org/software/bind

Free SMB/CIFS and AD/DC server and client for Unix

https://www.samba.org/

API for access to scanners, digitals camera, frame grabbers etc

http://www.sane-project.org/

Stand-Alone shell combining many common utilities

http://members.tip.net.au/~dbell/

Wrapper around libsass

http://libsass.org/

Scala Programming Language

http://www.scala-lang.org/

Scan_ffs recovers lost disklabel

High-speed Dirac codec

http://www.diracvideo.org/

ANSI C version of the SciMark2 benchmark

https://math.nist.gov/scimark2/download_c.html

Build tool alternative to make

https://scons.org/

Tiny shell that only permits scp and sftp

https://github.com/scponly/scponly/wiki

Converts the output of "vidcontrol -p" to PNG

Converts the output of "vidcontrol -p" to text

Multi-screen window manager

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

Small and lightweight screen(1) wrapper

https://sourceforge.net/projects/screenie/

Various X related scripts

https://cgit.freedesktop.org/xorg/app/scripts

Open Document Cataloging Project

http://scrollkeeper.sourceforge.net/

Interpreter for several adventure games

https://www.scummvm.org/

Cross-platform multimedia development API

https://www.libsdl.org/

Cross-platform multimedia development API

https://www.libsdl.org/

SDL graphics drawing primitives and other support functions

http://www.ferzkopp.net/Software/SDL_gfx-2.0/

Simple library to load images of various formats as SDL surfaces

https://www.libsdl.org/projects/SDL_image/

Sample multi-channel audio mixer library

https://www.libsdl.org/projects/SDL_mixer/index.html

Library to use TrueType fonts to render text in SDL applications

https://github.com/libsdl-org/SDL_ttf

SDL graphics drawing primitives and other support functions

http://www.ferzkopp.net/Software/SDL_gfx-2.0/

Simple library to load images of various formats as SDL surfaces

https://www.libsdl.org/projects/SDL_image/

Sample multi-channel audio mixer library

https://www.libsdl.org/projects/SDL_mixer/index.html

Small sample cross-platform networking library

http://www.libsdl.org/projects/SDL_net/

SDL_Pango is the SDL API to the Pango text rendering engine of GNOME 2.x

http://sdlpango.sourceforge.net/