Ah, I see the confusion. The power supply should be connected such that the positive terminal is on the left. If you look at the breadboard, you can see that this is, in fact, what's built. My description of the circuit's operation above is accurate when the power supply is properly connected.

Yeah, the LED in the opto isn't even connected correctly. I doubt it would ever light up. I left a post on the website explaining how it should have been setup.