My understanding is that the purpose of amateur licensing is to facilitate and encourage experimentation and learning, up to and including people building their own hardware; that's why the rules are about how your machine affects the world.
That's exactly right. I'm licensed by the FCC to build my own radio from a bucket of spare parts if I want to, and I can do whatever I want with it as long as I stay inside their rules. The RF I generate is what I'm responsible for. How I get there is up to me.
