Wrong. It is your determination that they must arrive at C that makes it a railroad.
All the rest is just details of laying rails.
If you were running a game instead of a railroad, then you would not be concerned with choosing the players' moves for them. You would not be rigging the outcome.
You would let the players play the game, and so discover the outcome.
You misunderstand me. I wasn't implying that the GM was forcing the players to go to C. I was assuming that the players
wanted to go there. That is, the GM has presented them with an adventure hook that requires their PCs to make their way to a particular destination (C) and the players have accepted the hook and their PCs have set off on the journey.
I can accept that if the GM only gives them a linear path with which to go from A to C, this does not automatically mean they're on a railroad. Even if the players aren't given the option to take multiple routes to their destination, as long as they can still affect the outcome (and not just of each individual encounter but also the overall plot), then there's no railroad. If the PCs' actions at B make the encounter at C easier or harder, then it's not a railroad. If the encounter at B makes it apparent to the players that it isn't worth their PCs' time to go to C and the GM is happy to let them go to D instead, then it isn't a railroad. But if the GM is determined that the PCs go to C no matter what, and even if he has given them several paths to get there, then it
is a railroad.
Going back to NWN2, I think perhaps my problem with that game is not that it's linear and therefore also a railroad. It's just that it happens to be both linear
and a railroad. On a small level, the game gives you choices and allows you to affect the outcome of particular encounters. For instance, depending on your Diplomacy skills and the dialogue choices you make, you might be able to circumvent a potential combat encounter. Or if you're very sneaky, you might be able to bypass it entirely. If you fail, you have to fight. But how you tackle each individual encounter has no bearing on the overall plot. Successfully talking your way out of encounter A has no effect on encounter B. Winning or losing the trial makes no difference because either way you're fighting the frenzied berserker, and if you fail
there, it's game over (or reset to your last saved game, as the case may be, since this is a video game). Even if you beat the guy, winning or losing the trial has no real effect on the environment. Sure, you get either a good title or a bad one, but that title carries very little meaning within the game. You can also insult your companions all you want, and they won't leave you (except at prescripted moments). And even if you don't bother to follow the various romantic subplots, the cut scenes assume you do (playing a female, you can ignore the paladin all you want and choose never to engage him in the romantic dialogue, but his actions in the cut scenes are all scripted as though you have).
Anyway, I realize this is a CRPG and not a tabletop game, so a certain amount of scripting is necessary. But like I mentioned in my original post, NWN1 gave you a lot more freedom than NWN2 does. And I think NWN2 can still be used as a good example of what a real tabletop RPG railroad looks like.