Apple has made several announcements regarding open source initiatives in conjunction with this week's Developer Conference:
Intel Kernel Sources "As of today, 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. We regret the delay in readying the new kernel for release, and thank you for your patience." More.
New "Mac OS Forge" for Community Projects "Mac OS Forge, a new community site hosted by Apple, is being created to support WebKit and other open source projects focused on Mac OS X, especially those looking to transition from OpenDarwin.org." More.
New Open Source Calendaring Server In order to encourage community participation, source code to the new iCal Server in Leopard Server is now available on Mac OS Forge under the Apache License. More.
Apache-Licensed Bonjour and Launchd sources "To further enable and encourage cross-platform adoption, the APSL** sources for Bonjour service discovery and Launchd process management are being re-released under the Apache License and hosted on Mac OS Forge." Bonjour, Launchd.