You get 5 activations per product key to activation on up to 5 computers of your choice. In order to activate it on 5 separate computers, each computer must have access to your user account at the point of activation; either offline or online activation. The computers do not need to be owned by the same person in order to do so, just have monetary access into your user account to activate and later down the road; access in order to be able to update.