What a strange article. Lots of words, but no clear meaning comes through to me. He seems to be taking one sentence from a Canonical license and saying that it proves there's lots of problems for open source because copyrights fwibble a gwabbit. Well, if he's making up stuff I might as well start making up stuff too. Copyrights are what keep open source open - i.e. you can't ignore the license and stop other people using the open source code you distribute without breaking copyright law yourself.
I really don't see the problem. Contributed code where copyright is assigned to the company can be distributed under a license specified by the company it was contributed to. How is this different from any other company that takes in code? Code that is already under the GPL stays under the GPL - you can't hijack it for your own license, thanks to the copyright laws. If Canonical start being bastards and distributing copyright-assigned contributed code under a non-free license then people will stop contributing. The stuff they have already distributed under a free license remains free forever and they can't revoke it.