Actually you have already been told, but anyway:
Debian:
-main repository consists of 100% free software, also the kernel is free of
firmware blobs since Debian squeeze. However, some packages in the main
repository _might suggest the installation of additional, non-free software_
like add-ons
- The Debian project hosts non-free repositories
Trisquel:
- repository and kernel consists of 100% free software; _no_ package suggests
the installation of non-free software, like add-ons or plugins.
- the trisquel project isn't involved at all with non-free software.
If you stick to the main repos, you don't have to check the packages, neither
on trisquel nor on debian.
If you use debian, you have to check the license of add-ons you might want to
install in certain programs like the webbrowser and you use the operating
system of a project that hosts non-free repos, which takes away people's
freedom.
Neither debian nor trisquel prevent you from installing non-free software on
your own (which you might have downloaded somewhere) but the repos are clean
(only the main repo, in case of debian).
