We offer Mathcad with two different options - Locked and Floating.  If you previously purchased Mathcad from a retail location you have a "Single User" License.  This is the difference between the different license types:

Floating - This is the most popular option for companies. With a floating license, you can install Mathcad on as many computers as you like.  When you startup Mathcad, the license will be activated with FlexLM technology.  If you have ONE Floating license, any person in your company that has the software installed on their computer can use Mathcad, but only ONE person can be using it at the same time.  A second user will not be able to use Mathcad until the first user exits the application. 
The floating license includes ALL of the 7 add-on modules, free 24 hour-5 day technical support and free upgrades. 

Locked - With a locked license, you will only be able to use Mathcad on one designated computer.  A locked license is registered to a company or individual and can be transferred from one computer to another.
The locked license includes ALL of the 7 add-on modules, free 24 hour-5 day technical support and free upgrades. 

Single User - A Single User license contains very minimal functionality (none of the 7 add-on modules) and was most likely bought at a retail location in the past.  A Single User license can not be transferred from one individual to another.  This type of license also does not include any technical support or upgrades.