It’s a song that has been named the most recognisable in the English language, but you may not believe that publicly singing it without permission requires you to pay.

The ‘Happy Birthday’ song is owned by corporate giant Warner Chappell Music, who earns around US$2 million in royalties each year.

Originally sung as ‘Good Morning to All’, the song was written by sisters Patty and Mildred Hill in Kentucky in the late 1800s. The song gained popularity, and birthday themed variations soon began to appear. In 1935, copyright was registered, eventually passing to Warner, whose rights in the song aren’t set to expire until 2030 in the US.

Filmmaker Jennifer Nelson was charged US$1,500 to feature the song in a documentary she produced about the song’s history. But now she wants her money back.

Two years ago Jennifer filed proceedings against Warner, saying she wants the song to be declared part of the public domain, and for Warner to return licensing fees dating back to at least 2009.

Recently, the case took an interesting twist – when a publication of the song was found in a 1922 edition of a children’s songbook (provided by Warner), without a copyright notice. (The brief of evidence can be viewed here)

Under the 1909 US Copyright Act, if a song did not indicate that it was copyrighted or use the © symbol, the published work would be placed irrevocably into the public domain. This version did not indicate any copyright, and is being used to argue that the song was in the public domain for at least ten years before copyright was even registered.

It is unclear what decision the court will hand down, but for now, the song is putting US copyright law in the spotlight.

The song is being used to demonstrate that reform to US copyright laws are desperately needed. Those dissatisfied with the US system argue that it is over-generous and outdated, claiming there is material from 1923 still under copyright protection until 2019.

Many also claim that copyright protection in the US has been hijacked by large corporations. Despite the fact that Warner donates hundreds of thousands of dollars from Happy Birthday royalties each year to a non-for-profit group called the Association for Childhood Education International, many corporations who own copyright in the US (including Warner) do not hesitate to pursue royalties from smaller companies, and continue to lobby for copyright terms to be extended (see Mickey Mouse’s influence on US copyright law here).

Australia’s system is slightly different and copyright protection of all published works will expire 70 years after the death of the owner. However, unpublished works in Australia have infinite copyright. We believe in balance, and that copyright protection remains necessary and important for protecting the work of local artists, writers, and musicians.

Click to read more from The Conversation, the Telegraph and the New York Times.