It would be amazing if there were a more open source option.
It's unfortunate that cars are so big and complex to manufacture. With a just as complex a set of regulatory systems around verifying their safety and roadworthiness. I really don't see something more open source being a realistic expectation at any foreseeable point going forward.
I mean, some parts of the protocols we use for the Internet need to be in the clear to work, DNS comes to mind. If you want that kept private as well you need to use something like tor.
But regardless, what people generally actually care about keeping secret is the content, not the protocol.