The kernel source was at http://android.git.kernel.org/ but that server was subsequently destroyed in an unrelated incident and at this point you'd need a time machine to verify that it was really there and hasn't just been backdated, but yeah, it was available.
Thanks for the links; they're convincing. I'm surprised that Google hasn't made their GPL compliance here more prominent. It's something I've heard criticized, but it sounds like the criticisms are illegitimate.
It still doesn't justify the "open source" moniker, but it's still good.