Re: Questions about legal theory behind (L)GPL
Actually, Effects v. Cohen is a prime example of "implied license as
an implied provision in the existing contract":
The district court initially dismissed the suit, holding that it was
primarily a contract dispute and, as such, did not arise under federal
law. In an opinion remarkable for its lucidity, we reversed and
remanded, concluding that plaintiff was "master of his claim" and
could opt to pursue the copyright infringement action instead of suing
on the contract. Effects Assocs., Inc. v. Cohen, 817 F.2d 72, 73 (9th
Cir.1987). We recognized that the issue on remand would be whether
Effects had transferred to Cohen the right to use the footage. Id. at
73 & n. 1, 74.
The court ruled for Cohen after finding exactly such an implied
license provision in the contract, and hence no copyright
infringement; Effects should have sued for breach of contract (Cohen
didn't pay the full agreed price).