Z:gnu-www-ja-fdl-howto-opt--4c2733-But that feature requires a sa/en

But that feature requires a safeguard to prevent it from being abused to endanger the free status of the manual. Person B who modifies a manual that was written by person A should not be able to make any of person A's documentation invariant, for that would deny person C the permission to modify it further. Likewise, if person B adds documentation for additional subtopics, this added documentation must not be invariant; the documentation itself must be modifiable by others. The FDL's conditions on adding invariant sections provide this safeguard.