"Mac OS X is based on the Mach kernel and is derived from the BSD implementation of Unix in NEXTSTEP. NEXTSTEP was the object-oriented operating system developed by Steve Jobs's NeXT company after he left Apple in 1985"
"Open source core system (APSL, GPL, others) with proprietary higher level API layers"
Ami szerintem érdekessék teszi a rendszert: Objective-C