"Jobs made a big point of the fact that Mach’s low-level kernel is open source. He sort of played down the flaw in the setup: Who cares if the basic operating system, the real low-core stuff, is open source if you then have the Mac layer on top, which is not open source? He had no way of knowing that my personal opinion of Mach is not very high. Frankly, I think it’s a piece of crap. It contains all the design mistakes you can make, and managed to even make up a few of its own.""