Basically, you need to have a licensed copy of whatever software you use on each computer that runs it simultaneously. So each workstation that you set up for your hands-on labs will need its own licensed copy.
Most of the 'starter' packages from the major manufacturers are limited to one package per customer, although some manufacturers will arrange special deals for educational institutions.
In the case of the AB package, it's available free for download, so presumably you can install it on multiple computers. Remember though, it is limited to the 10 I/O ML1000 models. It can't program the larger ML1000 models or any of the other MicroLogix products.