Warner/Chappell acquired the copyright - which was originally filed in 1935 - in 1988.
But judge George King ruled that the original copyright was only granted for specific arrangements of the music, not the song itself.
The tune was composed by two Kentucky sisters in 1893.
Mildred and Patty Hill called their version Good Morning To All, which later evolved into the song that is popularly sung at birthday parties around the world.
