Someone writing
the (GFDL) manual for the GF45 compiler might have invariant sections,
but won't be willing to copy my rant into his work; better to rewrite
the section then annoy half the users.
The fact that you're talking about a hypothetical example decades away
suggests that this is not a major issue. But we can consider the
issue anyway.
The scenario shows directly that this is an inconvenience, not a real
lack of freedom. The author of the GF45 compiler might prefer not to
use your regexp documentation, but he is free to use it, and using it
is feasible.
Any free software or free documentation license that has nontrivial
requirements can have results like this. For instance, there are
cases where people choose not to use a GPL-covered program because the
GPL has requirements that they don't want to follow. If you adopt the
stance that any license condition that someone might be reluctant to
follow is unacceptable, you'd have to reject most free software
licenses.
