"Apple's 10-year-old Mac OS X is a closed source operating
system with open source components.
"It is based in part on Darwin, an open source OS originally
developed by Apple in 2000 which incorporates code from Jobs'
NextStep, BSD and other free software, according to Wikipedia. The
BSD code in MacOSX, for example, includes the process model,
network stack, and virtual file system, the web encyclopedia also