Gerard writes:

When I talked to the Tropenmuseum about licensing their material, I asked Mike Godwin about this and I put this scenario explicitly to him. Material is licensed by a copyright holder, he can do it repeatedly in different ways for different levels of quality.

As I read this, Gerard represents my view accurately. It's important to remember that one aspect of (most) free licenses is that the original licensor retains many rights with regard to the copyrighted work. Granting multiple licenses to facilitate re-use in different contexts -- or different media -- seems to me to be one solution to the problem that Birgitte raises, which is that copyright is an area of law that treats very different media as if they were the same (it's a "kludge," all right), which means there are almost always going to be edge cases (statues, architectural plans, etc.) in which meeting the explicit requirements of a particular free license (such as CC-BY-SA) is going to be tricky.

That said, the efforts of Creative Commons to try to standardize on basic licensing language have done very much to make free culture freer -- by giving creators and licensors easier ways to talk about what kinds of rights they are trying to grant, and by increasing "interoperability" among freely licensed works.

--Mike