firmware-nonfree or linux-firmware-nonfree
' means that the software is bound to a license or copyright restrictions that impose limitations to your use and disposition: in short, it is not as free as the Gnu software to you, and that someday somewhere you not knowing what the license provisions over that is all about you can become illegal or something unlawful.
"FREE" in the world of Free and Open Source Software is all about "FREEDOM" and not necessarily like a "free beer" (buy me some if you have money
) Please read about it here
HOpe that helps.