Given Robert's stated reservation plus my note and the confirmation by
William Stein, I think that
others may share the view that GPLv3 is not acceptable, and perhaps "any
version of GPL"
is also not acceptable.
Maybe the project should be gplv1 or v2.
And if someone wants to use his/her code to fight patents etc, he/she can
make
a fork of maxima and stamp his/her contributions gplv3.