It's not complete. OS X also includes the user interface as a core part of the OS and, to be honest, I can't find it here.

Is this in some way different to Apple's normal open source offerings?

By which I mean, is there something new or interesting hidden on this page that I'm missing? :)

Nope.

It's the kernel and basic elements. When Steve Jobs introduced Mac OS X, he stated even then that its kernel would be open source.

Watch Steve Jobs state this here: http://www.youtube.com/watch?v=Ko4V3G4NqII

It's still great that Apple does this, nonetheless. More open than Microsoft.

(Similar source is available for iOS and some other properties too.)

Complete if complete = booting to a BSD command line. Otherwise, not even remotely complete. No Core services. No Finder. No DiskUtility or any number of other core OS binaries.

It's the Darwin repository. It's been up for years. It contains the OS X kernel and some command line utilities. What's the big deal here?