The boundaries of IP are as arbitrary as the boundaries of physical property. How much sound can you emit without it being considered aggression, how much molecules should be considered pollution, how much can your neighbor block the sun or how high can the airplane fly above. This is all arbitrary.
Obviously IP does not protect every word you produce. I see it as a form of NDA. If you produced certain information and condition the release of this information on certain actions, you should be able to do so., So for instance if you produce a software program you should be able to release it as a propery defined as the following: “Window 7 for use but not for sale”. So even though physically you release property that can be sold, officially, and logically you release only that part of the software which can be used but not sold. As far as I know this is how Rothbard saw it as well.