Just adding to @S'mon's reply:I have a simple question about the requirement of adding the term irrevocable to make a license like the GPL or OGL truly unable to be revoked. What is the court case that decided this in various common law jurisdictions?
I was told that this was an addition added only in the late 2000s.
And if that was the case, why? What were the circumstances that led the courts to rule this way? Because it is my understanding courts don't like to create sweeping changes. Instead, if they find a corner situation not handled by existing jurisprudence they tend to craft a ruling to handle that situation and no more.
There doesn't need to be a case establishing a "requirement" - it can be enough that a case expressed a view about how general interpretive principles might operate in respect of certain words and certain contexts, and so drafters decide its better to start including an express reference to irrevocability.