Welcome to Mac OS Forge!
>Mac OS X includes a wide variety of open source software from FreeBSD, NetBSD, OpenBSD, the GNU Project, and many more projects each its own vibrant developer community.Mac OS Forge is dedicated to supporting the developer community
surrounding open source components specific to Mac OS X.
Here you will find resources for working with the source code
to popular Apple-original projects, as well as third party projects
that are closely related to the Macintosh operating system.
というワケで、Intel版も含むDarwinはもちろん、launchdやらBonjourのソースも公開されてます。
ライセンスはApache License ver. 2.0。