"BNF itself emerged when John Backus, a programming language designer at IBM, proposed a metalanguage of metalinguistic formulas ... Whether Backus was directly influenced by Chomsky's work is uncertain."
Oh, lots of stuff gets invented multiple times, when it's "in the air". Nothing special about Chomsky here. And I wouldn't see that distracting from this particular achievement.
https://en.wikipedia.org/wiki/Backus%E2%80%93Naur_form
I'm not sure it required Chomsky's work.