Quote Originally Posted by Cybermonkey View Post
The kernel of MacOS on the other hand is based on (Free)BSD, another open source operating system ...
As far as I recall, Mac OS was initially proprietary project where Steve Jobs along with some other guys participated. Later, they've based Mac OS X on some portions of BSD in their NeXTSTEP, but correct me if I'm wrong, it still remains proprietary, isn't it?

Quote Originally Posted by Cybermonkey View Post
But why has Windows this huge market share? Because if one buys a computer Windows is pre-installed. So if Dell, HP and all others would install Linux, I think the market share of Windows would decrease rapidly.
"Why" is a much more complex issue. OEM distribution sure helps, but I bet there are historical reasons also. As a counter example, Asus tried to push Linux-based OS on their budget Eee PC line of netbooks, but many people formatted and reinstalled Windows there; now the entire Eee PC line uses mostly either Windows on Intel's platform and Android on ultra-portable line.