The DK GIS.RestrictedExtent function can be used to limit the extent of the map area that each user is allowed to view based on user password, etc.
While this feature might be useful to control a work process, it is not every effective to protect data distributed with a DK application. A user could still use another GIS program or application to access the entire map area (the distributed dataset). But, this technique could be effective with a web based GIS solution, such as developed from the TatukGIS DK.ASPNET edition (because then the data itself is not distributed to the user).