The author tries to answer the little moral question inside many number of people. Is it morally ok to use Apple software when you praise the open source itself?
It first starts with attacking Microsoft and depicting it as an evil company. Later on though the big question still remains, why use Apple when you have open source which is better than Apple's own software cause Apple's Aqua etc... are all closed. You see when people compare open source with Microsoft software they claim that open source is better because it is open. So that question remains with the Apple.
To answer the question the author shifts the position of the open source itself, instead of putting open source as a target, now the author claims that open source is not good for the sake of it, but it is good when you use it with closed source apps. He tries to hit the jackpot there, except the fact that his whole idea is based on making Apple look nice in open source.
There is no question that, you can enjoy open source on windows as much as you enjoy them on mac os x.
The article also begins with the false assumptions (or lies) about the migration of windows users. I wonder which scientific survey does the author depend on to make that claim? News.com? Register.com? Slashdot?