What you wrote is right...
... but we are not talking about culture (which is rarely licensed under the GNU FDL, and even more rarely present in the repository of a GNU/Linux distribution). We are talking about software documentation. RMS and the FSF believe that documentation ought to be free because it helps the user achieve a work (like a scholar manual, a cooking recipe, etc.). See this article, which also talks about the invariant sections and confirms what leny2010 was writing: However, it must be possible to modify all the technical content of the manual, and then distribute the result through all the usual media, through all the usual channels; otherwise, the restrictions do block the community, the manual is not free, and so we need another manual.
