"BFD" here means "big f#$%ing deal", not "b??? factorization domain".
"Bounded Factorization Domain" apparently
https://en.wikipedia.org/wiki/Atomic_domain#Special_cases
This is a pretty hilarious misinterpretation
> "Lambda calculus is a bounded factorization domain in the subfield of programming languages. What's the problem?"
This is a good example of abusing the vocabulary of mathematics as is common in the FP world. A programming language is not an object in abstract algebra. You can't add, subtract, or factorize a programming language. It's just software.