The current owners Warner/Chappell acquired the copyright originally filed in 1935 in 1988. The Judge George King ruled that the original copyright was only granted for a specific arrangements of the music not of the song itself.
Background
The ditty was written by two Kentucky sisters in 1893.
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Despite this ruling you still need to exercise considerable care when it comes to producing this song as the song stil remains a protected work under the laws of copyright.Â
Copy of the Judgment can be found here.Â
https://www.eff.org/document/happy-birthday-summary-judgment-order
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