Mapserver Itasca Application server is Thin Clients, that users can only command. Then the software will process out. And MapServer Itasca application users can only zoom in zoom, and out, pan and query for view information, but cannot be fetch out from the server. And the information is only the image data.
OpenLayers server is Thick Clients, that users can do many things. Users can render, display, query and process. OpenLayers is a server with real data. Not only the image data. Therefore, it can bring information to analyze in another program. Then, if disable network connect it can able to access a information.