> How about the software in the micro controllers in my car? Should I be allowed to modify that code too (if I mess up people could die)?

You're allowed to modify any other part of the car. Why should software be different?

> How about the software in my satellite internet radio transceiver (one rogue transceiver could take down the entire beam/jam the satellite)?

There can be some flexibility for the part of the code actually doing the transceiving.

Everything on top should be replaceable.

And radio is really a special case, because it's a shared commons that requires a lot of expertise and where one bad transmitter can cause problems for miles or more.

>How about the software in my satellite internet radio transceiver (one rogue transceiver could take down the entire beam/jam the satellite)?

This sounds like a failure on the satellite part. Can you do satellite comms with SDR?

>How about the software in the micro controllers in my car? Should I be allowed to modify that code too (if I mess up people could die)?

What if people die because you cannot modify that code?

The problem is physics. You have a bunch of people in fairly close geographic area transmitting to the same point in space on the same frequency band. One bad actor can interfere with everybody else's tx.

> What if people die because you cannot modify that code?

I think it's far better to trust unmodified safety critical code that's been tested than to trust Joe Blow's precariously modified braking code that allows his Honda Civic to drift around corners better.

That's what laws are for.