I happened to come across that clause last week and tracked down some humorous commentary by jslint's author:
Douglas: That's an interesting point. Also about once a year, I get a
letter from a lawyer, every year a different lawyer, at a company--I don't
want to embarrass the company by saying their name, so I'll just say their
initials--IBM...
[laughter]
...saying that they want to use something I wrote. Because I put this on
everything I write, now. They want to use something that I wrote in
something that they wrote, and they were pretty sure they weren't going to
use it for evil, but they couldn't say for sure about their customers. So
could I give them a special license for that?
Of course. So I wrote back--this happened literally two weeks ago--"I give
permission for IBM, its customers, partners, and minions, to use JSLint for
evil."