is that a word?) has nothing to do with copyright. A work passes into the public domain only when the creator explicitly places it into the public domain, or when its copyright expires. From copyright.gov :
For an anonymous work, a pseudonymous work, or a work made for hire, the copyright endures for a term of 95 years from the year of its first publication or a term of 120 years from the year of its creation, whichever expires first.
