A distinction must also be made between "non-free software" and "non-FSDG
software."
The "Free Software Definition" is how we determine if a piece of software is
free or not. This definition is at http://www.gnu.org/philosophy/free-sw.html
and is comprised of the four freedoms: the freedom to run, study, modify, and
share software. If you can do all four of these, without restriction (save
for the possible "copyleft" condition that you let people who receive copies
from you have the same four freedoms - but no other restrictions), it is
free. If you cannot, it is not free. What the software recommends, works
with, or depends on has no bearing on this definition. The Free Software
Definition applies to a single piece of software. Under this definition,
Mozilla Firefox is free because you can do all these things.
The "Free Software Distribution Guidelines" (FSDG) are the criteria that FSF
uses when deciding which distros they endorse. These guidelines are here:
http://www.gnu.org/distros/free-system-distribution-guidelines.html. The FSDG
is an extension of the free software definition that takes into account how
the software interacts with other packages on the system. Non-free software
is obviously non-FSDG too, but FSDG also requires that software not
recommend, work with, or depend too much on non-free software. If a piece of
non-free software is essential to the functionality of this software, it is
not FSDG, even though it may be free. The FSDG are criteria for distros, not
individual packages, and not users. So we, as users, are not obliged to
follow FSDG, even if we want to keep a fully free system.
This is the LibrePlanet list of packages which present issues for FSDG
distros:
http://libreplanet.org/wiki/List_of_software_that_does_not_respect_the_Free_System_Distribution_Guidelines
I feel like I need to keep saying this, but inclusion on this list doesn't
imply that the software in question is not free. Some of those are non-free,
others have non-free bits, others depend on non-free data or libraries,
others recommend or mention non-free programs (even a mention of the name of
a non-free program is enough to get it on this list, apparently), and still
others have no use except in conjunction with non-free programs. Because
Trisquel would indirectly be promoting non-free software if it included any
of these packages, as they were, it conflicts with the mission of Trisquel;
but you can use these packages (assuming they are free as defined by the free
software definition) and your system stays free unless you install a non-free
addition.
