Via some mechanism, you could in theory “talk to” the machine's generated AI system to ask it why it did what it did. But will the car manufacturer permit you to do so?

Does the public allow sale of a car that is not fully auditable? If not, the car manufacturer will permit you to do so.

And what of our legal tools? Does copyright apply? Does copyleft apply? If not, are there other ways to protect the commons of software being developed as others attempt to lock it down?

Yes, public regulation. Developers cannot be counted on to self-regulate each other.