Key word - speculation. Does anyone know for a fact that he has a fully functional machine in his garage? I doubt it - it seems like there's little proof that a functional machine even exists. He could have parts of it in his garage so long as it's not all put together and functioning - like if he was (still) working on it. Remember - there is no radioactive material involved. If the machine is broken, in parts, incomplete - there is no hazard.
I agree that his garage is probably not listed as a site of usage on his license. If he was actually producing x-rays in his garage I would think that's a HUGE violation of their license.