Open-source audio processing library

http://www.surina.net/soundtouch/

Set of fonts by Adobe designed for coders

https://github.com/adobe-fonts/source-code-pro

C/C++ and Java sources to HTML converter

https://www.gnu.org/software/src-highlite/source-highlight.html

Set of fonts by Adobe designed for user interfaces

https://github.com/adobe-fonts/source-sans

Set of fonts by Adobe designed for UI

https://github.com/adobe-fonts/source-serif

Japanese font by Adobe designed for user interfaces

https://github.com/adobe-fonts/source-han-sans

Simplified Chinese font by Adobe designed for user interfaces

https://github.com/adobe-fonts/source-han-sans

Traditional Chinese font by Adobe designed for user interfaces

https://github.com/adobe-fonts/source-han-sans

Japanese font by Adobe designed for user interfaces

https://github.com/adobe-fonts/source-han-serif

Simplified Chinese font by Adobe designed for user interfaces

https://github.com/adobe-fonts/source-han-serif

Traditional Chinese font by Adobe designed for user interfaces

https://github.com/adobe-fonts/source-han-serif

SOund eXchange - universal sound sample translator

https://sox.sourceforge.net/

Custom rulesets for SpamAssassin

http://wiki.apache.org/spamassassin/CustomRulesets

Highly efficient mail filter for identifying spam

http://spamassassin.apache.org/

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

http://freebsdspamd.sourceforge.net/

DSP library and software FAX machine

https://www.soft-switch.org/

Extremely memory-efficient hash_map implementation

http://code.google.com/p/google-sparsehash

General Framework for Developing Spatial Indices

https://libspatialindex.org/en/latest/

Spatial Extensions for SQLite

https://www.gaia-gis.it/gaia-sins/

Spawns fastcgi applications

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

Super fast C++ logging library

https://github.com/gabime/spdlog

Common interface to speech synthesis

https://devel.freebsoft.org/speechd

CLI and Go API to test internet speed using speedtest.net

https://github.com/showwin/speedtest-go

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

http://sphinxsearch.com/

Gtk client and libraries for SPICE remote desktop servers

https://www.spice-space.org/

Simple Protocol for Independent Computing Environments

http://www.spice-space.org

Standalone JavaScript based from Mozilla 102-esr

https://spidermonkey.dev/

Standalone JavaScript based from Mozilla 91-esr

https://spidermonkey.dev/

Bi-directional translation between SPIR-V and LLVM IR

https://github.com/KhronosGroup/SPIRV-LLVM-Translator

Tools for processing SPIR-V intermediate shader language modules

https://github.com/KhronosGroup/SPIRV-Tools

Monospaced bitmap fonts for Xorg and vt(4)

https://github.com/fcambus/spleen

Tool for statically checking sourcecode for security vulnerabilities

http://www.splint.org/

Japanese custom font based on Noto Sans and Lato

https://github.com/spoqa/spoqa-han-sans

The Spring Framework for Java

https://www.springframework.org/

Double entry accounting system

http://www.sql-ledger.org/

Lightweight database abstraction layer

SQLite backed FUSE file system

https://www.nongnu.org/libsqlfs/

SQL database engine in a C library

http://www.sqlite.org/

SQL database engine in a C library

https://www.sqlite3.org/

Set of tools to manipulate squashfs images

https://squashfs.sourceforge.net/

New set of tools and libraries to work with SquashFS images

https://infraroot.at/projects/squashfs-tools-ng/

Mount a squashfs archive and treat it like a local file system

https://github.com/vasi/squashfuse

HTTP Caching Proxy

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

Webmail system which accesses mail over IMAP

http://www.squirrelmail.org/

Library for serialising LV2 atoms to/from RDF

http://drobilla.net/software/sratom

Supplement file for lookup to use "Random House"

http://openlab.ring.gr.jp/edict/srd-fpw/

Secure Reliable Transport (SRT) Protocol

https://www.srtalliance.org/

Tool for computing context triggered piecewise hashes

https://ssdeep-project.github.io/ssdeep/