"If they show the license of the package is it possible to modify them so
that they warn you that you are trying to download a non-free package?"
Since Trisquel is not endorsed by the FSF, mere warning is not enough.
One of the criteria for keeping the endorsed status is that Trisquel:
"...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."
This should probably be discussed with the other FSF-endorsed distros on the
gnu-linux-libre mailing list as Trisquel is not likely to be the only one
that his impacts.
