I suppose it depends on your definition of "use."
For one of them, it's at the bottom of this web page. You must have missed
it: "Copyright © 2004–2018 The Trisquel Project | Otherwise noted, the
contents of this page are licensed under the GNU Free Documentation License
with no invariant sections."
For another definition of "use", they do have things like the GCC manual
which does. Because it contains things like the GNU Manifesto. But only the
Manifesto is invariant, not the entire GCC manual. I think I once read
somewhere that the Debian Project didn't want to accept the manual because
they can't change the GNU Manifesto. I wonder what they would change the GNU
Manifesto to say if they could.
So do you mean "use" in the sense of Trisquel-specific things that get made?
Or "use" in the sense that packages from others can be allowed in some cases?
Keep in mind that Trisquel couldn't accept an entire software manual that was
invariant because of the GNU FSDG:
https://www.gnu.org/distros/free-system-distribution-guidelines.html
"Information for practical use" includes software, documentation..."
"It does not include artistic works that have an aesthetic (rather than
functional) purpose, or statements of opinion or judgment."
"All information for practical use in a free distribution must be available
in source form."
"The information, and the source, must be provided under an appropriate free
license."
And so that allows the GNU Manifesto but not an entire software manual to be
invariant.
