The license keys are bound to the user. No issues with concurrent users. We do monitor the number of activation each user makes with each license and notify the him if it reaches a certain limit.
To Upgrade your license to your please follow the steps below:
1. goto http://iplotz.com/login.php and login .
2. once logged in to the admin account - goto http://iplotz.com/price.php and select the single user yearly license for one user and the 5 or 10 multi user yearly license for five or ten users.
3. You will be taken to the 'Upgrade Account' page and a discounted rate will be reflected in the cost of the license.
4. Enter the credit card details and Click 'Make Payment' button.