There is more to open source than source code. While it's useful to read sources, the real benefit comes from working with them to fix bugs, make enhancements, and install new versions on your system. Darwin, the open source core of Apple's Mac OS X operating system, contains hundreds of open source projects. In addition to the projects developed by Apple, many projects come from a wide variety of other open source initiatives, including GNU/Linux, FreeBSD, NetBSD, OpenBSD, XFree86, and independent projects hosted at SourceForge and elsewhere.

Because of the diversity of its component projects, and the unique requirements of the commercial Mac OS X system, Darwin's build system is quite different than the other open source initiatives listed above. If you are interested in building and modifying Darwin projects, the documentation on this website, and the DarwinBuild tools, will prove to be an invaluable resource.