The first oculus headsets used camera base stations to track the headset and controllers, all of the recent ones have used cameras on the headsets itself to track everything, these can be used to see the real world, however since they are infrared cameras meant for tracking there is no colour and the resolution isn't as high as it should be for AR to be useful.
I had the first oculus, and it didn't have any base stations. It didn't track anything at all, in fact... it only detected rotational motion of your head, it didn't detect any other motion at all. There also were not any controllers.
The "dev kits" were freely sold to everyone and also bought by consumers, not just developers. Very different to sell-your-soul-NDA'd console devkits given out to select studios. "early adopter edition" would have been just as fitting.
Because even though they called it a dev kit, it was still a commercial product in many ways... there were a ton of games released for it, and a whole community of users who were not oculus developers. I got one, and I never wrote any software for it nor had any real plans to. I got it purely as a consumer.
