John August, quoting Paul Collins’ larger story for Slate:
If you write a scene in which characters sing “Happy Birthday,” prepare to write a check:
Its copyright retains an eternal power to provoke incredulity: Really? I have to pay for that? But Warner Music Group, who acquired it in 1988, collects upward of $2 million a year from film and TV fees off the song.
The copyright is almost certainly lost, but Warner keeps being paid because it’s considered too costly to fight them in court over it.