This was a bit of a surprise to me, but Apple released the xnu-2782.40.9 source code – among others – used in Yosemite 10.10.5 No idea if this happened before – not that I recall – but a new update of Yosemite may soon be released. Otherwise this is a totally unexpected move from Apple.
Oh and a new version of kext tools (384.30.2) is also available for download. Too bad that this isn’t the latest. Oh well. We can’t have everything at once.