I think this article misses the point, and I think it goes wrong right about here:
The GPL is a license. It deals with copyright law. It defines who is allowed to copy & distribute the software (everyone).
The GPL "deals with" copyright law, but that does not mean that all of its force relies upon copyright law, nor does it mean that the definition of "derivative work" in copyright law has any bearing on the problem at hand.
The GPL is a license, granting users the right to use the software. So, we can use WordPress, because the author allows us to (by means of the GPL).
The GPL puts restrictions on our use. Among these, that if we wish to produce any derivative works (under the GPL's definition of "derivative"), we must also release these under the GPL. As far as I can tell, copyright law has nothing to do with this restriction.
Actually, it does. The GPL is a copyright license, which means its only restrictions derive from copyright law. It can't prevent activities otherwise allowed by copyright.
> The GPL is a license, granting users the right to use the software. So, we can use WordPress, because the author allows us to (by means of the GPL).
The GPLv2 (the version in discussion here) explicitly denies that it covers running software:
Activities other than copying, distribution and modification
are not covered by this License; they are outside
its scope. The act of running the Program is not
restricted
There is no such restriction. You are legally allowed to produce derivative works, without releasing the source to anybody. The catch is to do so, you must not distribute the derived work in a way which requires copyright permission. Once you distribute a derived work, copyright (and thus the GPL) applies.
This means, I then assume, that the usage of WordPress (for example) is regulated solely via the "Terms and Conditions" for WordPress, and the GPL is not a factor?
If that's the case, couldn't WordPress simply add a line to their "Terms and Conditions" stating that all access to WordPress functions via Themes are limited to those themes released under the GPL?
This is not quite correct, in my opinion.
Copyright only applies to your work, and works which are derivative works according to copyright.
You can't write a license that requires someone to release 'all' his work under the GPL, for example. (It may be different if it's a contract.)
That's just what the FSF wants you to think. Of course, it usually doesn't pay to go through the legal hassel to defend yourself from unjustified claims by the FSF -- thus it's an effective chilling strategy.
For more information, see http://www.law.washington.edu/lta/swp/Law/derivative.html
Has something like this ever happened?
Don't like the GPL? Don't use it; it's just that you then fall back on standard interpretations of "derivative work", which -- you'll find, are at least as restrictive.
8 notes are enough to constitute derivative work for music, as are 4 paragraphs. I'm not aware of specifics for code, but I believe they'll be even less comfortable for you than any gpl interpretation.
Two lines of Perl, two for Python, 10 keystrokes for Lisp and a region of 1000 pixels of Smalltalk, given standard fonts as shown on a class browser. About a hundred lines for Java or C# ;-)
If, however, it is based on an example template or shares non-trivial code with it, then it's derivative work and should be under the GPL.