Microsoft has gradually changed the way Dynamics AX has been licensed from a concurrent user and module model to a server license and CAL (Client Access License) model.
For example, in Dynamics AX 1.5 through to 4.0, you would determine with your partner the modules that you need and how many concurrent users you will require. As your use of the software progresses, you can buy additional functionality or additional users that become unlocked by a license key.
The technical control of this in Dynamics AX is very elegant. If features are not available in the license, the user interface elements simply do not appear. MorphX (the technology that AX uses to generate the user interface) will draw the forms dynamically, laying out the available fields and buttons in such a way that there will be no clue that a set of fields, buttons, and other elements have been hidden from the form.
The model of only licensing the functionality you need, although common in the industry, has some undesirable effects. Customers would tend to buy only what they absolutely need, opting not to buy "nice to have" modules which potentially detract from the solution the partner is trying to provide and deterring the customer from making the most of the software as they grow.
The new server and CAL licensing model enables all of the functionality provided by Microsoft Dynamics AX, placing a restriction on the number and type of users instead. This means customers using AX 2012 are far more likely to make broader and better use of AX than those with any previous version.
To allow AX to be used cost effectively throughout the organization, Microsoft has split the CAL into four categories, each with a different price. These CAL types map standard security roles based on the functionality that the roles enable:
By default, you must license Dynamics AX using named user CALs, purchasing the appropriate CAL type for each user that has access to Dynamics AX regardless of how many are logged in at any one time. This model is fine for users who make extensive use of the system but could be prohibitively expensive in situations where many different users will access a small amount of AX functionality via a shared device, for example, in a warehouse or call center.
To address this, Microsoft also allows you to buy a Device CAL. Device CALs are intended to be used where multiple users access AX from the same physical device (for example, a warehouse dispatch terminal or mobile device). In this case, you buy an access license for each device at the required level instead of per user. When you purchase AX licenses, you do so based on the above license types as a named user or device.
You also need to buy a minimum of one server license and potentially more depending on how your solution was sized.
Note
The preceding information is accurate at the time of publication, but licensing does vary from time to time. So you should always consult the licensing guide available at http://www.microsoft.com/en-us/dynamics/erp-buy-ax-software.aspx.