Free software programmed in C

ZSNES is an emulator for the Super Nintendo Entertainment System released as free software. There are official ports for Linux, MS-DOS, Windows, and unofficial ports for Xbox, and macOS.

HTTP accelerator software

open source software driver for Nvidia GPU

Virtual machine designed to run various dynamic programming languages

Liferea (short for Linux Feed Reader) is a news aggregator for online news feeds and podcasts. It supports the major feed formats including RSS/RDF and Atom and can import and export subscription lists in OPML format. Liferea is intended to be a fast, easy to use, and easy to install news aggregator for GTK+ that can be used with the GNOME desktop. Liferea features a script manager, in which users can add custom scripts that run whenever a certain action occurs.

framework for multilingual input

The '''Linux Audio Developer's Simple Plugin API (LADSPA''') is an application programming interface (API) standard for handling audio filters and audio signal processing effects, licensed under LGPL-2.1-or-later. Originally designed through consensus on the Linux Audio Developers mailing list, it now works on a variety of platforms. It is used in many free audio software projects, and there is a wide range of LADSPA plug-ins available.

ffdshow is an open-source unmaintained codec library that is mainly used for decoding of video in the MPEG-4 ASP (e.g. encoded with DivX or Xvid) and H.264/MPEG-4 AVC video formats, but it supports numerous other video and audio formats as well. It is free software released under GNU General Public License 2.0, runs on Windows, and is implemented as a Video for Windows (VFW) codec and a DirectShow filter.

open-source Microsoft Silverlight implementation

GROMACS is a molecular dynamics package mainly designed for simulations of proteins, lipids, and nucleic acids. It was originally developed in the Biophysical Chemistry department of University of Groningen, and is now maintained by contributors in universities and research centers worldwide. GROMACS is one of the fastest and most popular software packages available, and can run on central processing units (CPUs) and graphics processing units (GPUs). It is free, open-source software released under the GNU Lesser General Public License (LGPL) (GPL prior to Version 4.6).

musl is a C standard library intended for operating systems based on the Linux kernel, released under the MIT License. It was developed by Rich Felker to write a clean, efficient, and standards-conformant libc implementation.

software library that provides line-editing and history capabilities for interactive programs with a command-line interface

PearPC is a PowerPC platform emulator capable of running many PowerPC operating systems, including pre-Intel versions of Mac OS X, Darwin, and Linux on x86 hardware. It is released under the GNU General Public License (GPL). It can be used on Windows, Linux, FreeBSD and other systems based on POSIX-X11. The first official release was made on May 10, 2004. The software was often used to run early versions of OS X on Windows XP computers.

XEmacs is a graphical- and console-based text editor which runs on almost any Unix-like operating system as well as Microsoft Windows. XEmacs is a fork, based on a version of GNU Emacs from the late 1980s. Any user can download, use, and modify XEmacs as free software available under the GNU General Public License version 2 or any later version.

Bacula is an open-source, enterprise-level computer backup system for heterogeneous networks. It is designed to automate backup tasks that had often required intervention from a systems administrator or computer operator.

MLDonkey is an open-source, multi-protocol, peer-to-peer file sharing application that runs as a back-end server application on many platforms. It can be controlled through a user interface provided by one of many separate front-ends, including a Web interface, telnet interface and over a dozen native client programs.

library for arbitrary precision arithmetic, operating on signed integers, rational numbers and floating point numbers

free software that corrects and cleans up HTML and XML documents by fixing markup errors and upgrading legacy code to modern standards

daemon application designed to take care of the user's security credentials

fast, small and free C compiler

software installation application for the GNOME desktop environment

HAProxy is a free and open source software that provides a high availability load balancer and proxy (forward proxy, reverse proxy) for TCP and HTTP-based applications that spreads requests across multiple servers. It is written in C and has a reputation for being fast and efficient (in terms of processor and memory usage).

Privoxy is a free non-caching web proxy with filtering capabilities for enhancing privacy, manipulating cookies and modifying web page data and HTTP headers before the page is rendered by the browser. Privoxy is a "privacy enhancing proxy", filtering web pages and removing advertisements. Privoxy can be customized by users, for both stand-alone systems and multi-user networks. Privoxy can be chained to other proxies and is frequently used in combination with Squid among others and can be used to bypass Internet censorship.

virtual network switch

PhotoRec is a free and open-source utility software for data recovery with text-based user interface using data carving techniques, designed to recover lost files from various digital camera memory, hard disk and CD-ROM. It can recover the files with more than 480 file extensions (about 300 file families). It is also possible to add custom file signature to detect less known files.

console screen editor

iperf, also known as Iperf or iPerf, is a tool for network performance measurement and tuning. It is a cross-platform tool that can produce standardized performance measurements for any network. iperf has client and server functionality, and can create data streams to measure the throughput between the two ends in one or both directions. Typical iperf output contains a time-stamped report of the amount of data transferred and the throughput measured.

graphics library

CinePaint is a free and open source computer program for painting and retouching bitmap frames of films. It is a fork of version 1.0.4 of the GNU Image Manipulation Program (GIMP). It enjoyed some success as one of the earliest open source tools developed for feature motion picture visual effects and animation work. The main reason for this adoption over mainline GIMP was its support for high bit depths (greater than 8-bits per channel) which can be required for film work. The mainline GIMP project later added high bit depths in GIMP 2.9.2, released November 2015. It is free software under th

XBoard is a graphical user interface chessboard for chess engines under the X Window System. It is developed and maintained as free software by the GNU project. WinBoard is a port of XBoard to run natively on Microsoft Windows.

e2fsprogs (sometimes called the e2fs programs) is a set of utilities for maintaining the ext2, ext3 and ext4 file systems for the Linux kernel. Since those file systems are often the default for Linux distributions, it is commonly considered to be essential software.

TortoiseGit is a Git revision control client, implemented as a Windows shell extension and based on TortoiseSVN. It is free software released under the GNU General Public License.

2003 video game

thumb|Christian Grothoff, maintainer of GNUnet, in [[Berlin on August 1, 2013, at the "#youbroketheinternet. We'll make ourselves a GNU one." event]] GNUnet is a software framework for decentralized, peer-to-peer networking and an official GNU package. The framework offers link encryption, peer discovery, resource allocation, communication over many transports (such as TCP, UDP, HTTP, HTTPS, WLAN and Bluetooth) and various basic peer-to-peer algorithms for routing, multicast and network size estimation.

LibreSSL is an open-source implementation of the Transport Layer Security (TLS) protocol. The implementation is named after Secure Sockets Layer (SSL), the deprecated predecessor of TLS, for which support was removed in release 2.3.0. The OpenBSD project forked LibreSSL from OpenSSL 1.0.1g in April 2014 as a response to the Heartbleed security vulnerability, with the goals of modernizing the codebase, improving security, and applying development best practices.

libvirt is an open-source API, daemon and management tool for managing platform virtualization. It can be used to manage KVM, Xen, VMware ESXi, QEMU and other virtualization technologies. These APIs are widely used in the orchestration layer of hypervisors in the development of a cloud-based solution.

Eggdrop is a popular IRC bot and the oldest that is still being maintained.

TightVNC is a free and open-source remote desktop software server and client application for Linux and Windows. A server for macOS is available under a commercial source code license only, without SDK or binary version provided. Constantin Kaplinsky developed TightVNC, using and extending the RFB protocol of Virtual Network Computing (VNC) to allow end-users to control another computer's screen remotely.

email client

FreeMat is a free open-source numerical computing environment and programming language,

desktop environment for X Window System

libjpeg is a free library with functions for handling the JPEG image data format. It implements a JPEG codec (encoding and decoding) alongside various utilities for handling JPEG data. It is written in C and distributed as free software together with its source code under the terms of a custom permissive (BSD-like) free software license, which demands attribution. The original variant is maintained and published by the Independent JPEG Group (IJG). Meanwhile, there are several forks with additional features.

vsftpd (or very secure FTP daemon) is an FTP server for Unix-like systems, including Linux. It is the default FTP server in the Ubuntu, CentOS, Fedora, NimbleX, Slackware and RHEL Linux distributions. It is licensed under the GNU General Public License. It supports IPv6, TLS and FTPS (explicit since 2.0.0 and implicit since 2.1.0).

BRL-CAD is a constructive solid geometry (CSG) solid modeling computer-aided design (CAD) system. It includes an interactive geometry editor, ray tracing support for graphics rendering and geometric analysis, computer network distributed framebuffer support, scripting, image-processing and signal-processing tools. The entire package is distributed in source code and binary form.

GNOME front-end application for managing PGP and SSH keys

libpng is the official Portable Network Graphics (PNG) reference library (originally called pnglib). It is a platform-independent library that contains C functions for handling PNG images. It supports almost all of PNG's features, is extensible, and has been widely used and tested for over 28 years. libpng is dependent on zlib for data compression and decompression routines.

open source web server software application

The GLib Object System, or GObject, is a free software library providing a portable object system and transparent cross-language interoperability. GObject is designed for use both directly in C programs to provide object-oriented C-based APIs and through bindings to other languages to provide transparent cross-language interoperability, e.g. PyGObject.

supporting library for the Apache web server

Sylpheed is an open-source e-mail client and news client licensed under GNU GPL-2.0-or-later with the library part LibSylph under GNU LGPL-2.1-or-later. It provides easy configuration and an abundance of features. It stores mail in the MH Message Handling System. Sylpheed runs on Unix-like systems such as Linux or BSD, and it is also usable on Windows. It uses GTK+.

is a package of utilities distributed by the Linux Kernel Organization for use in a Linux operating system. A fork, (with meaning "next generation"), was created when development stalled, but has been renamed back to , and is the official version of the package.

Xarchiver is a front-end to various command line archiving tools for Linux and BSD operating systems, designed to be independent of the desktop environment. It is the default archiving application of Xfce and LXDE. Deepin's archive manager is based on Xarchiver.

access remote or virtual systems

Polkit (formerly PolicyKit) is a component for controlling system-wide privileges in Unix-like operating systems. It provides an organized way for non-privileged processes to communicate with privileged ones. Polkit allows a level of control of centralized system policy. It is developed and maintained by David Zeuthen from Red Hat and hosted by the freedesktop.org project. It is published as free software under the terms of version 2 of the GNU Lesser General Public License.

descriptive vector graphics language

Shadowsocks is a free and open-source encryption protocol project, widely used in China to circumvent Internet censorship. It was created in 2012 by a Chinese programmer named "clowwindy", and multiple implementations of the protocol have been made available since. Shadowsocks provides an encrypted equivalent of a SOCKS proxy. A Shadowsocks client converts the Shadowsocks connection to SOCKS5 for local use. Unlike an SSH tunnel, Shadowsocks can also proxy User Datagram Protocol (UDP) traffic.

free text editor for dynamic programming languages

Uzbl is a discontinued free and open-source minimalist web browser designed for simplicity and adherence to the Unix philosophy. Development began in early 2009 and is still considered to be in an alpha state by the developers. The core component of Uzbl is written in C, but other languages are also used, most notably Python. All parts of the Uzbl project are released as free software under GNU GPL-3.0-only.

libxml2 is a software library for parsing XML documents. It is also the basis for the libxslt library which processes XSLT-1.0 stylesheets.

libavcodec is a free and open-source library of codecs for encoding and decoding video and audio data.