Could someone tell me why we would want to do unpaid labour for Microsoft?
I'm quite prepared to test and help support Linux and open source projects. Microsoft? Not so much....
I'm sure the Linux distro makers (which often are commercial entities) gladly take your free labor, and laugh at their way to bank.
The phrase is actually, "laugh all the way to the bank".
In any event... You imply that I can't use Linux to make money without selling it. That's pretty silly.
I make a pretty good living using Linux, in spite of neither paying nor receiving any money for Linux, and I am quite sure I'm far from being the only one. Why should I care that the maintainers of my distro sell a commercial version of it? They're not taking any money from me, and they've bills to pay same as most folks, including me, so it's all good. I conclude that you're ignorant and/or trolling.