You should execute /applic/nir/sun4/mcad.b/bin/mcad (without the sun4 once the directory is moved to the solaris application disk). This is a script which configures some environment variables used my mathcad.

The Mathcad license server needs to be run on the OS server. For some reason it doesn't verify license requests from dataless clients running Solaris. Check my Mathsoft mail file for appropriate license keys.