@this is largely bollocks
Actually, I reckon it's completely bollocks, and has been ever since these numbers first started being circulated.
Who supplies the world's most widely used servers? Compaq (well, HP if you must), and to be specific the Proliant range.
What OS does it come with?
Let's read that again, loudly so Tim can read it too: NO OS IS SUPPLIED BY DEFAULT WITH A PROLIANT SERVER.
So how do the nice people at Gartner and IDC know what all these servers are running?
At the low end, it'll be a mix between Windows SBS, and a Linux. Windows SBS may or may not be sold with the server but a Linux almost certainly won't, the Linux part of a Linux/Proliant sale is invisible.
At the high end, it'll be a mix between Windows and Linux. The high end customers will have their own software supply arrangements with MS or an MS reseller, so even if it's a Windows/Proliant sale, the Windows part of the sale is invisible. And once again so is the Linux part of a Linux/Proliant sale.
In the middle of the market, who knows.
Until proven otherwise, these are nothing more than made up numbers.
But please don't tell anyone that the emperor has no clothes, as he may then catch cold.