Why Microsoft will offer an Open Source OS
You can accuse Microsoft of many things, but not making lots of money isn't one of them. If Linux ever got to the point where it was costing the company serious money, what's to stop MS from fighting like with like? As Mat says: "They've already been accused of making money from other people's ideas, why would they stop with open-source software that they can provide support for, if it ever becomes an overwhelming hit?"
But the conclusion we reached was that, although Microsoft could indeed produce a free OS if it wanted to, the situation won't arise, simply because Linux will never pose a genuine threat.