It's perfectly fine for me to develop programming skills by reading any code regardless of the license. When a corp snatches an employee from competitors, they get to keep their skills even if they signed an NDA and can't talk about what they worked on. On the other hand there's the no-compete agreement, where you can't. Good luck making a no-compete agreement with a neural network.
Even if someone feeds stolen or illegal data as an input dataset to gain advantage in ML, how do we even prove it if we're only given the trained model and it generalizes well?