Interesting article.
It's actually a hypothetical letter from the year 2008.
In the letter, it says that Bill Gates hired Linus in the year 2005 to build an OS (WinX) based on open-sourced Linux. Turns out this was a brilliant move and, while MS has lost its monopoly on the OS market, they're still doing just fine - and Windows isn't crap anymore. Steve Ballmer, though, is still stuck in the 2005-MS mentality of 'proprietary monopoly or nothing!' - which is, obviously, where MS (including Gates) is at right now.