WARNING Obsolete:

Atalasoft newer versions no longer support Silverlight web controls. Supports ability to assist in keeping existing Silverlight deployments working may be limited. No further fixes/updates will be issued for our Silverlight assemblies/controls

Main Article

The Atalasoft SilverlightImageViewer requires a DotImage Photo Pro or Document Imaging web deploy license. While testing from localhost you can use your developer or evaluation license. Once deployed to the real web server you will need to purchase a server license.

This license must be placed in the same folder as the web project that is hosting the Silverlight control. 

Original Article:
Q10284 - INFO: Running the Atalasoft Silverlight Demo