Can MapViewer display map layers generated from another WMS server?
Yes with 10.1.2. For details please see the answer to this question. That solution will not work if you are using MapViewer version 9.0.4 or earlier. You can, however, employ the following partial solution. MapViewer lets you specify an arbitrary URL to a background image, through the bgimage attribute of a map request. Construct a valid GetMap request to a WMS server, and use it as the value of the bgimage attribute. MapViewer will then display the result map as its background.