The folks at Debian-legal are having a discussion of the GNU Free Documentation License. At least some members think the license does not meet their "free" test. At issue is the ability to use the license to declare portions of a doc "invariant", meaning they cannot be modified down the line. From the FSF explanation:
The idea of invariant sections is that they give you a way to express nontechnical personal opinions about the topic.The classical example of an invariant nontechnical section in a free manual is the GNU Manifesto, which is included in the GNU Emacs Manual. The GNU Manifesto says nothing about how to edit with Emacs, but it explains the reason why I wrote GNU Emacs--to be an essential part of the GNU operating system, which would give computer users freedom to cooperate in a community. Since the GNU Manifesto presents the principles of the GNU Project, rather than features of GNU Emacs, we decided that others should not remove or change it when redistributing the Emacs Manual.