The number of activations I feel is unlimited. However, you must first deactivate Datacad on your working computer and then re-activate Datacad on your other selected machine.
An alternative is to contact Datacad, with your user names and secret codes etc and request that they deactivate Datacad for you. With one licence, you can only have one computer working with Datacad at any one time.
This system has never failed me ever since softlocks were introduced.