Where you would probably cross the line is you sold this as a service. Doing this for personal use is one thing, selling your apartment's antenna connection over the internet to a single other person is another.
In both examples I am renting space in which to place my antenna. In the first example, I own a single antenna and pay fees to my landlord. In the second example, I own a single antenna and pay fees to Aereo. I would argue that the only difference is marketing.