Tom Lehrer is a pretty cool old dude - he released a statement on November 1, 2022:
I, Tom Lehrer, and the Tom Lehrer Trust 2007, hereby grant the following permissions:
All copyrights to lyrics or music written or composed by me have been relinquished, and therefore such songs are now in the public domain.
In short, I no longer retain any rights to any of my songs.
So help yourselves, and don’t send me any money.
Go grab those sound files, lyrics, and sheet music while you can: tomlehrersongs.com.
I have definitely been humming:
"Once the rockets are up, who cares where they come down? That's not my department!" says Wernher von Braun.
Ok, now I'm off poisoning pigeons in the park, bye bye.