Although the song "Happy Birthday to You" was written in the 1800's, Time Warner/Warner Music claims that it's still under copyright and demands royalties each time it is publicly performed. While its copyright status is doubtful, Warner still collects $2 million per year in royalties.
There was a contest to come up with a royalty-free alternative. It's not good. Sadly, "It sounds like Radiohead made a birthday dirge and left out their trademark happy-go-lucky pep." So it looks like Warner will keep getting its royalties.