I just saw this story over at slashdot.
“There’s some considerable argy-bargy in progress over whether or not GNU’s own GFDL is a Free documentation license at all. At issue are “invariant sections” which cannot be removed from derivative works.”
It took me about 60 seconds to read the relevant portion of the GFDL to see that someone has the wrong end of the stick.
“A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document’s overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.
The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none. “
In other words if, for example, you were to write a book entitled “Hacking The GIMP“, license it under the GFDL, and include a section stating “The author is not a developer of the GIMP and cannot guarantee that your copy of the program will continue to work after following the instructions in this book.”, you could declare that section as invariant. This seems perfectly reasonable to me.
Without the invariant section a later author could take your work and modify that section to read “The author guarantees your GIMP will run faster and better after reading this book.” A trivial example, but without the ability to mark the given section that “deals exclusively with the relationship of the publishers or authors of the Document to the Document’s overall subject (or to related matters)” as invariant a more serious subject matter could land an author in a lot of trouble as a result of someone’s (legal) modification of the text.