What is an Old-School RPG?

Jay 'Rampant Coyote' Barnson muses on the subject of old-school RPGs and what makes them that in his latest blog post, of which I'm going to quote a snippet:
For example. turn-based vs. real-time (or (action)). Action-based, (real-time) RPGs have been with us for a very, very long time. I like to refer back to Gateway to Apshai, published in 1983 (yeah, over a decade before Diablo), which was pure action-arcade-RPG. You had the trappings of an RPG, gathering loot and gaining levels as you used the joystick to do action-based battle against pixellated bad-guys. We can also go back to Ultima III or Telengard, two of the earliest CRPGs I ever played. These were (real-time turn-based) if that makes any sense. You had time limits to choose your actions. Worse, the only (pause) command was getting into some input loop where the games were asking for additional details or confirmation of your action.

So really, as far as I'm concerned, and as much as I like to refer to (turn-based) games as (old school), the truth of the matter is that both have been with us about as long as we've had commercial CRPGs. There's absolutely nothing inherently new or improved or better about action-based gaming. And there were absolutely no technical limitations preventing RPGs from being real-time / action based back in the day, Mr. Findley. (Hopefully he's repented of that attitude now that they're working on Wasteland 2). There were lots of action-RPGs back then.

...

We can't even agree about a time-period for (old-school.) Maybe it's my age, but I still have a tough time thinking of any game published in a year that begins with a (2'³ as (old-school.) It's like. for me, you take the history of commercial computer games, which for me begins around 1979, and mark it at the halfway point between then and now which would be about 1996 and set that as the (old-school) demarcation. Yeah, I'll give it a little bit of extra slosh, but I have a tough time thinking of a game like Oblivion as old-school. Friggin' kids. Plus, as I'm a retro-gamer who is still playing older games for the first time (I just recently finished Knights of the Old Republic II: The Sith Lords), I have a tough time thinking of some of these games as being all that old.