Re: [Trisquel-users] what repositories in debian 8 are free software?

[taiji_tao]

If the goals is FSF libre, then only use main.  As onpon pointed out contrib  
contains a mixture of free and non-free.  Virtualbox is an example, it is  
free, but uses a non-free installer.  You could use 4.1 or older and have a  
libre version as well.

You could also, review the license of each program before installing,  
however, this can be tricky as some programs are free, but the documentation  
might not be...