Apple has an open-source framework for developing drivers on Mac OS X called the I / O Kit.

* I / O Kit – an open-source framework from Apple for developing Mac OS X device drivers

Currently Mac OS X programmers can choose between limited IDEs, including native IDEs like Xcode, older IDEs like CodeWarrior, newer IDEs like MyEclipse, and open-source tools, such as Eclipse and Netbeans.

* Sequel Pro-a free, open-source front end for Mac OS X.

TPlus is an open-source implementation of original ( non-OO ) Turing with systems programming extensions developed at the University of Toronto and ported to Linux, Solaris and Mac OS X at Queen's University in the late 1990s.

As of 2008, there are more than 50, 000 third-party applications available for the Palm OS platform, which have various licensing types, including open-source, and various closed licensing schemes such as freeware, shareware, and traditional pay-up-front purchase.

In 2000, Rhapsody was forked into Darwin and released as open-source software under the Apple Public Source License ( APSL ), and components from Darwin are present in Mac OS X today.

For example, Mozilla Firefox, an open-source web browser, is available on Microsoft Windows, Mac OS X ( both PowerPC and x86 through something Apple calls a Universal binary ), and Linux on multiple computer architectures.

* Pixen is free, open-source, and available for Mac OS X.

* ASEPRITE is free, open-source and available for Windows, Mac OS X and Linux.

The Fink project is an effort to port and package open-source Unix programs to Mac OS X. Fink uses dpkg and APT ( Debian's package management system ), as well as its own frontend program, ( which is implemented as a set of Perl modules ).

* Audacity is a free and open-source digital audio editor that can run on Mac OS X, Microsoft Windows, and Linux ; it is particularly popular in the podcast community, and also has a large following among the visually impaired due to its keyboard interface.

* Q ( emulator ), open-source x86 emulator for Mac OS X

An open-source RISC OS port of Doom has emerged from Jeff Doggett, which supports Doom, Doom 2, Ultimate Doom and FreeDoom game files.

A long-standing third-party commercial alternative named Resorcerer remains available, and more recently there have been a number of attempts to build open-source Mac OS X-native resource editors, including one called ResKnife.

* Excalibur ( software ), an open-source, LaTeX-aware, spell-checker for Mac OS X

* WW2D was a cross-platform, free and open-source application based on Java and OpenGL technologies and can be run on Microsoft Windows, Mac OS X, Linux ( x86 and x86-64 ) and Solaris on SPARC.

In 2001, under severe financial pressure due to too much leverage, BSDI sold its software business unit ( comprising BSD / OS, plus the former Walnut Creek involvement in the FreeBSD and Slackware Linux open-source projects ) to Wind River Systems and renamed the remainder iXsystems, with plans to specialize in hardware.

An open-source project called Pentagram aims to create an engine capable of running Ultima VIII on modern operating systems, most notably Windows, Mac OS X and Linux.

Tomboy is a free and open-source desktop notetaking application written for Unix-like ( including Mac OS X and Linux ) and Microsoft Windows operating systems, written in C # using Gtk #.

AAT font features are supported on Mac OS 8. 5 and above, including OS X and also on several open-source operating systems such as Linux via IBM's ICU library.

On June 11, 2005, version 0. 1 was released, with all proprietary technology replaced by free and open-source alternatives, with the result that the game now runs on GNU / Linux, Mac OS X and Windows.

Colloquy is an open-source IRC, SILC, ICB and XMPP client for Mac OS X. Colloquy uses its own core, known as Chat Core, although in the past it used Irssi as its IRC protocol engine.

The browser was notable among BeOS users due to its haiku error messages, which lead to the name of Haiku, an open-source BeOS clone.

Haiku began as the OpenBeOS project in 2001, the year that Be, Inc. was bought by Palm, Inc. and BeOS development was discontinued ; the focus of the project was to support the BeOS user community by creating an open-source, backward-compatible replacement for BeOS.

With its roots in market research, ' competitive intelligence ' has been described as the ' application of principles and practices from military and national intelligence to the domain of global business '; it is the business equivalent of open-source intelligence.

Rhost is free, but not open-source.

" Mozilla " is the every-day name for the free and open-source software project that was founded in 1998 in order to create a next-generation Internet suite for Netscape.

An open-source license is a copyright license for computer software that makes the source code available for everyone to use.

Free software and open-source are two similar categories of software licensing but which criteria of inclusion has open source including a few more licenses than is allowed under the free software definition.

" The Open Source Definition " is a document published by the Open Source Initiative, to determine whether a software license can be labeled with the open-source certification mark.

Red Hat, Inc. () is an American software company that is engaged in providing open-source software products to the enterprise community.

The term shareware is used in contrast to retail software, which refers to commercial software available only with the purchase of a license which may not be copied for others ; public domain software, which refers to software not copyright protected ; open-source software, in which the source code is available for anyone to inspect and alter ; and freeware, which refers to copyrighted software for which the developers solicit no payment ( though they may request donations ).

Usually, shareware differs from free / open-source software in that requests of voluntary shareware fees are made, often within the program itself, and in that source code for shareware programs is generally unavailable in a form that would allow others to extend the program.

Free / open-source software is usually compatible with the strict Association of Software Professionals shareware guidelines.

The open-source Mozilla project is incorporating SMIL and other XML-related technologies such as SVG and MathML into their browsers.

An argument sometimes used against open-source security is that developers tend to be less enthusiastic about performing deep reviews as they are about contributing new code.

Combined with the fact that open-source is dominated by a culture of volunteering, the argument goes, security sometimes receives less thorough treatment than it might in an environment in which security reviews were part of someone's job description.

Open Turing is an open-source implementation of the original Turing interpreter for Windows written by Holt Software.

OpenT is an abandoned open-source language, compiler, and IDE that was being developed by the members of the dTeam of Computer Science Canada.

Apple's iPod does not natively support Vorbis but through the use of Rockbox, an open-source firmware project, is capable of decoding Vorbis files on certain models.

The open-source Mika VM aims to implement JavaME CDC / FP, but is not certified as such ( certified implementations are required to charge royalties, which is impractical for an open-source project ).

KDE's open-source KHTML engine is used in KDE's Konqueror web browser and was the basis for WebKit, the rendering engine in Apple's Safari and Google's Chrome web browsers, which is now the most widely used browser engine according to StatCounter.