Which version of the GPL? Because there are several, and in the Torvalds talk linked above, he points out that the different versions have different intentions.
> Canonical's uncooperative and unclear stance towards the community
Uncooperative and unclear? The 'flat refusal' linked in the main article is pretty clear and cooperative. "Do this thing at this link and we'll be cool with it, and we have a track record of being so". Sounds clear and cooperative to me.
> whose contributions enable it to exist
This is the kind of shit I mean above when I say pissing on allies. You're painting ubuntu as a parasite rather than an ally. Ubuntu has done plenty to help the community and is part of that community - in particular, they took making a non-techie friendly desktop and driving that goal forward as their specialty. Do they do everything perfectly? No, but none of the major players do.
I mix debian and ubuntu in my work, and the debian/FSF purists really puzzle me sometimes. One friend of mine read mjg's comments on the same issue on lwn and bought it hook, line and sinker. Started arguing with me that there was zero difference between Apple and Canonical, simply because although Canonical provide you with their source code, you need a little more elbow-grease to make a derivative of their whole integrated environment (which is a violation of a very liberally-read 'freedom 2', apparently). You're free to make that derivative, but it's just not as simple as removing one package. Apparently this makes them the same as a corporation famous for it's industrial secrecy and lockdown of user capabilities, and who has had the police raid someone's home because they thought one of their prototypes was there. It's a ridiculously binary view of the world.