I'd say it's patent law, not copyright law, that make the licences possible to enforce.
Most of the patents are the result of a lot of research and cleverness. Some of the patents are the equivalent of looking in another drawer if the first one did not contain what you are looking in.
It's a bit arbitrary that an API isn't protected when some bullshit patents are. There is clearly much thought in some of the java APIs.
I'd like to see shorter protection time for patents thought, especially in areas where there are very low investment costs, like software development.
For the rest there is the 3GPP patent platform.