I disagree slightly with this. If you absolutely cannot afford the 100 and whatever dollars that it takes to buy Windows and you'll either download Windows for free (but you'll use, say, the free Windows store money from Bing to buy apps) or download Linux for free, I'm ok with stealing a copy of Windows. I (and I assume Microsoft too) would rather someone spend, say, $20 in the Windows ecosystem as opposed to downloading Linux and spending none. Obviously Microsoft would prefer you buy Windows THEN spend $20 on apps, but something is better than nothing and some people just cannot afford it.
(as a disclaimer, I fully admit to legally buying 100% of my copies of Windows)