Not using radioactive materials and not making dangerous radiation wold be enough to stop inspectors from interfering.
Sure, it would.
But... If Rossi actually developed nuclear reactors - that is - something generating energy from nuclear reactions - this would be subject to stringent checking and testing from every possible angle. Rossi CLAIMING there was no radiation, there were no radioactive materials would not cut it.
So the question is whether when Rossi sells this new heat source everyone believes its power comes from nuclear reactions. Difficult to see how that could be avoided?