And then there's the wrinkle of trademarks. Look and Feel is certainly in the realm of trademarks, and I'm sure that 37 signals has their designs trademarked, and their logos, and "getting real", and everything else they've ever created.
Intellectual property laws are interesting. It's a giant game, moreso than crime or other torts, since everything is made up with little basis in physical reality. I'm not opposed to the idea, but it's fun seeing the law operate in a self-created vacuum.
Another example (and similar to the one you mention) is Carl Malamud's public.resource.org - he's taking WestLaw's court records, removing the copyrighted bits, and publishing them himself online. The problem then becomes how to cite them, since WestLaw's numbering system is somewhat of a de factor standard.
All-in, you're quite right - this is nowhere near as clear as the article thinks it is, and it's certainly not a domain that I'd rely on a non-lawyer's opinion for.