> There isn't a similar degree of legal risk with MPL 2.0, nor with non-copyleft licenses (which is the subject of this subthread, not proprietary licenses)

There is a similar degree of legal risk with the overwhelming majority of licenses in use. Yes, using exclusively permissively-licensed software would let you avoid this particular risk - but given that essentially no-one (BSD advocates are, if anything, less scrupulous about avoiding proprietary software than GPL advocates - you rarely hear of BSD-land pushing firmware into a separate nonfree repository or the like) does that, it's clearly not a risk many people care much about.