You are wrong. Where do you think that Novell and RedHat get the Linux that they sell?
Do you think that Linus Torvalds burns them a CD and has his reindeer deliver it?
Nope. Sorry. RedHat and Novell get the latest Linux by downloading it off of the Internet.
Are they stupid enough to download some unsupported software from the Internet to run critical business and end up losing millions? No way.
Why not? Considering how wonderfully secure and stable the software that they've bought from Microsoft has been, it can't be much worse.
Everyone knows that buying software costs make up but a very small percentage of the total costs of running computers.
Well, that depends. For business computers, that's somewhat correct. For home computers, software, especially Windows, is now over 25% of the cost of a system and continues to grow. It continues to grow for business computers, but since the hardware and administration are the lion's share of the expense, it's not as big of a part.
The difference in the admin costs really stand out. Linux is less expensive to run. Yeah, there are some studies that say differently, but when you read the fine print, those studies never include cleaning viruses, worms, spyware, fixing broken patches and other Microsoft-isms.
Trying to save pennies by downloading free OS from the Internet would be really stupid
It's not about saving pennies. It's about getting something that works for a change.