In 1998, Congress extended the terms of copyright for works published before 1978 from 75 years to 95 years. In practical terms, this meant that works of art first published in the United States in 1923—which would otherwise have entered the public domain in 1999—got an extra 20 years of copyright protection. On Tuesday, those twenty years will finally be over, and a large number of movies, books, songs, paintings, and at least one work of choreography (Ellen Tels’ Persisches Ballett ) will be entering the public domain for the first time. That means anyone will be able to adapt them, perform them, remake them, or publish them, and we can expect a wave of new editions and free digital versions of a wide variety of Jazz Age art in the new year. There are some real treasures in the mix, particularly in film: work from Buster Keaton ( Three Ages , Our Hospitality ), Cecil B. DeMille ( The Ten Commandments ), and Harold Lloyd ( Safety Last ) will belong to all of us in just a few days. In...