That is the letter of the law, yes. I would suggest though that the spirit / intent behind the law includes fostering a community, which in turn encourages open and clear communication.
No, the legally binding licenses that fall under the purview of Copyleft enforcement. A critical component of modern Free Software is licenses that absolve the primary author of liability that is implicitly agreed-upon when contributing third-party code. If these contributors disagreed with the terms of the GPL then they had 30 years to realize it.
What specific law are you talking about?