Fair use means legally using a copyrighted material without requiring permission of the copyright holder. It does not mean you can redistribute in general, though some forms of redistribution are fair use, such as using an excerpt from a book in your essay.
Reverse engineering code is also fair use, but that doesn’t mean it’s fair use to share the code you’ve reversed.
I’m wrong about why,
But it’s been ruled as fair use
That says reverse engineering is ok – not sharing RE’d code.
AFAIK fair use means you can redistribute.
Fair use means legally using a copyrighted material without requiring permission of the copyright holder. It does not mean you can redistribute in general, though some forms of redistribution are fair use, such as using an excerpt from a book in your essay.
Reverse engineering code is also fair use, but that doesn’t mean it’s fair use to share the code you’ve reversed.