
IANALBILTPIA also. Imagine that. Anyway, assuming that you did not agree to the terms of their license, you would be violating copyright. However, since it is apparent that they've actually distributed it under a GPL, and merely added those terms and conditions to the front, rather than distributing it under a modified GPL, no, you would only be violating the DMCA.
Oh, and at least one other poster might be interested to know that a trademark need not be registered, and given the recent usage of the term, 'Open Source' would almost certainly qualify for being an unregistered trademark, if it were unregistered. Now, I wouldn't be willing to bet that the term is, in fact, unregistered, also given recent usage of the term.
Now, one bit of confusion I do have, as IANAJ, and most specifically, IANTJThatThisCaseWouldGoToIfItWereTakenToTrial, and, of course, said trial hasn't happened yet, is does the fact that the author of the code is attempting to add terms to the GPL modify the effect of the attempt? If that detail doesn't modify the attempt, then, as someone said above, the additional restrictions simply fall off. If it doesn't, then, well, as someone else above mentioned, none of us use it, because humans are animals, and we therefore all produce various animal products - whether software, cars, noxious gasses, or other...