Active display is a Motorola thing and as far as I know uses additional hardware to pulse without creating wakelocks. Ambient display is a Google thing and it has only 2 functions, wake up the display when a new notification arrives or wake up the display when the device is picked up. All that can be achieved on any modern smartphone with existing sensors (maybe with a sensor hub, ala Apples M8, for better power optimization) .
So the only difference is that Google will wake you display at pickup while Apple will not. Therefore saying "so implementing something like that" isn't an egregious statement, maybe not 100% correct, but close enough for discussion sake.
Nokia Glance is closer to Active display then Ambient display. Ambient display is more like what Apple is doing +1 little feature.
Ambient display functionality description:
That is all a bit of speculation, since we aren't still sure if Ambient display will be in the AOSP or are they trying to make up for the missing LED or even taking advantage of additional HW Motorola put in there. Ambient display is not mentioned as a function on the Android 5 page.