Apple ships Leopard's Darwin code
Apple has released the Darwin source code behind its Leopard operating system to developers.
Darwin 9.0 forms the backbone of the UNIX-based operating system and is being made available to developers in the open source community, as it has been since Mac OS X 10, the first version of the OS. Darwin 9.0 is a fully-conformant UNIX operating system that's built on Mach 3.0 and FreeBSD 5. It bundles over a hundred popular Open Source products, including bash, tcsh, ksh, and zsh, emacs, vim, and nano.