In September, a judge ruled that music licensor Warner-Chappell doesn't own the copyright to "Happy Birthday." The question now seems to have become who does?

A charity called the Association for Childhood Education International (ACEI) has now stepped forward to say that if Warner loses the copyright, it should become the rightful owner. Earlier this week, ACEI filed court papers (PDF) asking to intervene in the copyright dispute.

ACEI has been receiving one-third of the licensing revenue Warner generates from Happy Birthday, estimated to be around $2 million per year. The charity is the sole shareholder of the Hill Foundation, an organization set up by song author Patty Hill and her sister Jessica to collect royalty revenue from the song. Royalty payments from Happy Birthday "represent a substantial portion of the Organization's yearly budget."

"It is now likely that Applicants are the valid owners of the copyrights to the Song, and none of the current parties are able to adequately represent Applicants’ interests," wrote ACEI lawyers.

A filmmaker filed suit to challenge the validity of the Happy Birthday copyright in 2013. In September, US District Judge George King ruled that the Hill sisters never transferred any rights to Summy Co., a music publishing company later acquired by Warner/Chappell.

King didn't invalidate the copyright altogether, although he expressed doubts about whether the Hill sisters wrote the song at all and when they wrote it. The Hills are widely acknowledged to have sold a song with similar lyrics, "Good Morning to You," to Summy Co. in 1893.

While King definitively nixed Warner's claim to Happy Birthday, the song isn't in the public domain. As Techdirt, which first reported the ACEI filing, points out, the song instead is a kind of "orphan work."

The judge in the case sees the issues around authorship as being unclear enough that they may require a trial.

Newspapers reference the singing of a Happy Birthday song in 1901 and 1909, and "Happy Birthday" appeared in a songbook in 1911 without crediting anyone with the lyrics. Songbooks from 1911 and the 1920s published the work without a credit, with one exception, and were copyrighted by other authors. Patty Hill never publicly claimed she had written "Happy Birthday" until she was deposed in a 1935 copyright lawsuit.

One possibility is that Hill wrote the song and then waited 40 years to take credit for it. On the other hand, it's possible that someone else wrote Happy Birthday, and "Patty’s 1935 claim to authorship was a post hoc attempt to take credit for the words that had long since become more famous and popular than the ones she wrote for the classic melody," King wrote.

Meanwhile, Warner/Chappell has filed a motion (PDF) asking the judge to reconsider his earlier ruling against them.