Debian is not a GNU FSDG[1] (Free System Distribution Guidelines) distro, so
its packages do not necessarily meet the requirements outlined in the FSDG.
The FSDG requires all packages to be free software as a baseline requirement,
but then imposes additional requirements on top of that. One of these, for
example, is the requirement that "A free system distribution must not steer
users towards obtaining any nonfree information for practical use, or
encourage them to do so. The system should have no repositories for nonfree
software and no specific recipes for installation of particular nonfree
programs. Nor should the distribution refer to third-party repositories that
are not committed to only including free software; even if they only have
free software today, that may not be true tomorrow. Programs in the system
should not suggest installing nonfree plugins, documentation, and so on."
There are probably numerous packages in Debian that, although are technically
free[2], are not FSDG compliant, since that isn't (unfortunately) a mission
of Debian's. Iceweasel is one such example; although it is a rebranded
Firefox (and hence is free software itself) it uses the Mozilla addons
repository which does contain non-free extensions, thereby rendering
Iceweasel non-FSDG. By contrast, Trisquel's Abrowser uses Trisquel's own
addons repository which has the same free software requirements Trisquel
itself has.
Plenty of people in the Trisquel community (and probably the wiser
GNU/Linux-libre community) tend to conflate non-free and non-FSDG together,
since neither of them are desirable for a GNU FSDG system such as Trisquel.
[1] http://www.gnu.org/distros/free-system-distribution-guidelines.html
[2] http://www.gnu.org/philosophy/free-sw.html
