Of course not! They're public domain so no restrictions on how they're used. I would like to see screenshots of how you use them if you wouldn't mind sharing. I'm on Twitter or the Pixeland discord server.
Oh, we haven't started yet. We're learning to make 3d First Person Narrative games and needed to find public domain assets. I came across this set and found them very interesting, even shaping what kind of story I could write.