I agree that different kinds of licenses are appropriate for different kinds of works. I am writing the GNU Free Documentation License for documentation--that is, for manuals. It is also a good license for any sort of textbook. For some kinds of works, such as fiction, permitting just verbatim copying is good enough in my opinion. For other works, permitting unlimited citation with attribution is good enough.
However, it is very important that the license used for documentation and textbooks *not* contain an option which would make it too restrictive for documentation and textbooks. Such an option would encourage people *writing documentation and textbooks* to use the option and make them non-free. Instead of offering the authors of other works an extra complicating option in a license meant for documentation, it is better if those authors use simpler alternative licenses.
