"When Apple announced that it was moving Mac OS X to the Intel
platform, one thing that didn't get much attention was that Apple
would not be open-sourcing the Intel Darwin kernel. Now, Apple has
reversed its course and has quietly announced that it will
open-source the kernel after all.
"In a note to the Darwin developer's list, Apple's open-source
project manager, Ernest Prabhakar, wrote, 'As of today [August
7th], we are posting buildable kernel sources for Intel-based Macs
alongside the usual PowerPC (and other Intel) sources, starting
with Mac OS X 10.4.7...'"