Philly,
You have a valid point about..
...2. Access HBO on another TV in the home that is not on his UVerse...
That's what HBO Go is really for IF the person also subscribes to regular HBO.
Certainly legit.
If you had mentioned in your post that you wanted to view older HBO content on your regular I wouldn't have commented. I wasn't the only one who wondered why you just didn't plug in UVerse.
And yes, unless you have some equipment problem, you can plumb HBO Go from your laptop to your big screen. I just did it last night as a test. You have to use or at least should use the Thunderbolt dongle to an HDMI cable. I guess if your TV doesn't have a spare HDMI port, you could use a VGA dongle.
I sure you know there is no AirPlay option yet for laptops and even if there was, you would then also need an ATV2 or ATV3. The last time I checked you can also NOT use AirPlay from a iPad or an IP (again, an ATV is also required). If you try that method, either the sound or the video doesn't Airplay because HBO doesn't allow it with their iPad or IP app. Probably concerns about theft of service whereas they can't controll "mirroring".