@grillchen Trisquel doesn't contain or recommend proprietary software in either the repos or the documentation.
You you have the freedom to install proprietary software in Trisquel, but that's kind of the same freedom as the freedom to shoot yourself in the foot - clearly it's wise not to do that.

Gentoo recommends proprietary software in the install guide, in the documentation and contains many ebuilds that install proprietary software
Although portage has the ACCEPT_LICENSE feature, the default "@FREE" accepts all licenses approved by the FSF and the "Open Source Initiative", which ends up accepting the numerous proprietary software licenses the "OSI" has approved.
At least 1/4 of the packages also have the wrong license listed - even GNU software where the license is a short --version or --license away or clearly documented on the project website.

It's possible to use Gentoo and retain your freedom, but you need to fight for it - as the developers keep trying to take it off you.