It began life as 'Good Morning to All' in the 1893, composed by Mildred J. Hill with the lyrics written by her sister, Patty. It was first published in 1912, but without credits or copyright notices. However, the Summy Company registered the song for copyright in 1935, crediting the authors Preston Ware Orem and Mrs. R.R. Foreman.

Warner/Chappell then purchased Summy in 1988 for $25 million, with 'Happy Birthday' at this time worth $5 million. Up until now, the song has earned Warner around $50 million in total and based on the 1935 registration, the copyright wouldn't expire until 2030 — or so they hoped. But it didn't last that long: the copyright has been found to be "invalid".

It is now ruled to be in the public domain, with music and lyrics so ubiquitous that it simply cannot be rationally copyrighted any longer. The ruling came from District Court Judge George King in the case of Rupa Marya, et al. v. Warner/Chappell, the group of musicians suing the latter back in 2013 and claiming that Warner didn't hold any rights to the song whatsoever.

Said Judge King:

"Accordingly, Defendants’ Motion is DENIED, and Plaintiffs’ Motion is GRANTED as to the issue of whether Summy Co. ever received the rights to the Happy Birthday lyrics from the Hill sisters."

He went on:

"In fact, Defendants cannot even point to evidence showing that the Hill sisters transferred their rights in the lyrics to the Hill Foundation, such that the Hill Foundation could, in turn, legitimately transfer them to Summy Co."

Marya, who previously had to fork out $455 because the audience sang 'Happy Birthday' on a live album, told AP: "I hope we can start reimagining copyright law to do what it’s supposed to do — protect the creations of people who make stuff so that we can continue to make more stuff."

Warner/Chappell are yet to say whether they'll appeal the decision or not.

Read the story of the copyright claim and more about this particular case here (pdf).