"You call BSD a kernel, it technically is a set of APIs" If you read that in context of the Mac Os X operating system, then it would be true, as there is a BSD

"You call BSD a kernel, it technically is a set of APIs" If you read that in context of the Mac Os X operating system, then it would be true, as there is a BSD "layer" or "part" in the XNU kernel. So if it had been written in that aspect/context, it would have been correct.