Sorry for those of you who don’t want to hear it but if a company like Criterion decides to restore a public domain film and releases it there is no way they can copyright their “restored version”. Think about what restoration is for a second…you can’t copyright something just because you put it back to the way it was supposed to be.
So to answer suspiciouscoffee’s original question yes you can take their restoration of Night of the Living Dead rip it and do whatever you want with it.