Applications :: How Does Adobe Updater Work

I recently purchased a used macbook and the previous owner left a copy of Photoshop CS 4 on there for me (I don't know if that is kosher or not). But I'm planning on buying the entire Creative Suite by next year, but it is a perk for me to have access to Photoshop for the time being.

I'm paranoid about losing access to Photoshop though, so I never update it with the Adobe updater for fear of it asking me for the serial # or it sensing a different IP or whatever it could do. But last night I allowed it to update the updater. Everything works fine still. I just allowed it to update itself, the actual updater program.

So i have a few questions:

1. Can people legitimately sell a mac with third party software still on the machine, such as Adobe Photoshop in my case?

2. When I allowed Adobe Updater udate itself from 6 version 6 to 6.0.2, did it talk to Adobe at all with regards to Photoshop, or is that too far of a stretch?

3. If I allowed the Updater to update Photoshop, would it check the serial # or anything at that point, or was the initial installation all there is to liscensing?

I'm asking this out of curiosity and because if I am in flagrant violation, I'd rather not be using the program. I'm paranoid about this type of thing too.