THIS week saw something that hasn’t happened in decades. On 1 January, the US copyright protection on a host of books, films, sheet music and artwork expired. Works from 1923, including silent movie The Ten Commandments and Charlie Chaplin’s film The Pilgrim , have now entered the public domain.

These works were granted a copyright extension by a 1998 law signed by US president Bill Clinton that retroactively added 20 years’ protection to works created in 1923 and later. That time is now up. …