im by no means a legal expert but on the face of those exact words
posted in the OP, there is nothing there that relates to software
freedom - they are only limiting use of their branding - this is
practically speaking the word "firefox" for example, and it's logo
images - neither of which qualifies as "works of practical use" per the
GNU free software definition - which says only that the same principals
of software freedom maybe "extended to a definition of free cultural
works"l but that it is not necessarily so - in this light, the mozilla
branding situation is more analogous to a free game with non-free art
assets to which the FSF has no objection - debian, on th other hand, has
a strict policy regarding the freedom of art assets; but the FSF is far
more lenient about such "non-functional data" - for this reason, i think
that the mozilla branding restrictions were never a major reason for
the re-branding of iceweasel, icecat, and abrowser in the way that it
was for debian
if this message had gone only to the FSD mailing list i would have
assumed that the intention was to suggest that firefox be endorsed or
otherwise not disparaged by the FSF, to which i would probably agree;
but noticing that this exact message went to the trisquel list, it would
seem the intention is to suggest that FSDG distros carry firefox by name
AFAIK, debian has no specific permission for use the "firefox" brand;
but the controversy was ended when mozilla determined that debian's
changes were not significant enough to require re-branding - i think the
changes in iceweasel, icecat, and abrowser are more significant though -
but even if they were not, i think that parabola would still prefer the
iceweasel name as it has acquired a reputation for freedom consciousness
and probably as well, icecat and abrowser are happy to continue branding
as they have done for so many years