You can call Red Hat “proprietary” all you want. That doesn’t make it true.
The difference between Red Hat Enterprise Linux bits and CentOS bits is virtually nil; we make all of our source RPMs available to anyone who wants them. (Ask Novell if they do the same. I’ll save you the time: they don’t.) What is “proprietary” is the brand, and the quality of service you are entitled to receive by being a paying customer. Oh, and the notion that “the price is the same whether you’re Goldman Sachs or a startup in Rio de Janeiro” is ludicrous.
If you want to duplicate that quality of service for Ubuntu users, that’s noble and admirable. That’s competition. But leave the FUD at the door, dude. You’re better than that. Aren’t you?
(Also posted as a comment to Mr. Shuttleworth’s blog. We’ll see what his response is.)