It is fairly straightforward, the cables and software are made by ross tech, so have a look round the site.
http://www.ross-tech.com/
The licence is built into the cable,so dont see why you cant use it on multiple computers, but i have never tried that. There isnt a separate dongle, as it is all just the cable.
The chineese clones are copies, and come with a hacked version of the software. The official software checks the serial number of the cable against a blacklist and will disable some of the clones if they dont have protection against this, so avoiding the internet is advised. Obviously the hacked version doesnt do this.
And yes you can use it on multiple cars.