A judge must avoid all impropriety and appearance of impropriety. This prohibition applies to both professional and personal conduct. A judge must expect to be the subject of constant public scrutiny and accept freely and willingly restrictions that might be viewed as burdensome by the ordinary citizen.
https://www.uscourts.gov/judges-judgeships/code-conduct-united-states-judges
Not that SCOTUS is held to the same code of conduct that all other federal judges are held to, of course.
He seems to be confusing "freeware", which is basically a license for copyrighted work, with "public domain", which is the absence of a copyright.