Statute vs. Contract law
In most cases, the grant of rights under a license obtained from the copyright owner is a waiver of the right to sue for infringement.
Remember, it isn't necessary for a copyright owner to use a software license (at all) or to permit anyone else to exercise one of the 'exclusive rights' to copy and distribute the software, make derivative works, and etc.
Having some sort of attribution inserted into derivative works isn't one of the exclusive rights enumerated in USC Title 17, section 106:
http://www.law.cornell.edu/uscode/html/uscode17/usc_sec_17_00000106----000-.html
The only exception is a case where the scope of the exclusive right(s) granted in the license are limited (e.g. GPL prohibitions against additional license restrictions or binary linking), and the licensee actually exceeds the scope of the license. That situation could result in both copyright and state-law claims for relief. This particular license had no such limitation on the 'so-called' exclusive rights.
A license can contain many additional terms and conditions that don't pertain to the 'exclusive rights'. Those are not preempted by the federal statute. Claims involving those terms and conditions are decided according to the applicable law of contracts.
Biting the hand that feeds IT
