I think Apple like open source, seehttp://www.apple.com/opensource/http://www.opensource.apple.com/release/mac-os-x-104/
But they had problems with bad hackers, so they closed the main system. At the beginning of os x, apple wanted an open system, what I know.
Apple makes systems that even old people and technology disinterested people can use. At the same time if you are familiar with UNIX you can make very much. Especially the install and uninstall of drivers and programs is easier than Linux. Also, the update of the system is very easy. In comparison to Linux. I think.
In addition, there are no Photoshop-like program for Linux, what I know.
Have tried on two computers now, Windows 7 and I became almost mad. I was Happy with Windows XP and 2000, but Windows 7 is really nerve-wracking.
E.g. external hard drive is usually only recognized as USB1 on WIN7, with os x as USB2.
Installing software without a certificate, in a normal way is not possible.
Same DVD burner on OSX without problem on Windows 7 same DVD is unreadable. E.g..
My grandfather don't use his expensive Windows computer, no longer. For him computer are time killer.
A ipad with a connection to the plasma TV would be the best for him, maybe. I don't know if that works.
But now for him, computers are now no longer interesting, although he was very skillful, for his age.
He wanted to cut very simple videos, slide show and write emails, no more. But the Windows computer always has had some pop up window. They asking him things, he could not answer. E.g. Do you want perform an update. Or, I found a suspicious file, should it deleted, etc.
Or the disk driver was faulty so the hard drive only 4 MB / s delivered.
Unfortunately now, most inexperienced computer users buy Windows. Although Apple has built the first PC.
And then they give up the computer or have done so difficult to understand the Windows system. That they make only the most necessary at the computer and any change in the workflow disturbed there mind. Thus, the are no longer willing to switch to another operating system.