Consumers typically pay cable companies extra fees for these boxes, and the cable industry is opposed to the effort.
Stream has raised the hackles of net-neutrality advocates because using it doesn't count against the data caps that Comcast has in some areas — they think this could make customers prefer Comcast's own TV service over, say, streaming Netflix, which would count against a cap.
Net neutrality is the concept that internet service providers should treat all traffic equally.