> That's not legal use of the material according to most copyleft licenses.

That probably doesn't matter given the current rulings that training an AI model on otherwise legally acquired material is "fair use", because the copyleft license inherently only has power because of copyright.

I'm sure at some point we'll see litigation over a case where someone attempts to make "not using the material to train AI" a term of the sales contract for something, but my guess would be that if that went anywhere it would be on the back of contract law, not copyright law.