You can install and use the trial version on as many computers as you wish. However, once the trial period expires you must purchase one license for each computer on which you wish to continue using SignGo. You will automatically receive a discount for additional licenses.
If you choose to buy SignGo you can install SignGo on as many computers as you like. SignGo will run on any of those computers so long as the USB dongle is inserted. This means you can run SignGo on any number of computers but only one at a time.