.CAS File

The cas file extension is associated with the AutoCAD and Revit Architecture CAD modeling applications developed by Autodesk.

A .cas file contains cascade license validation data for used for network installation of AutoCAD, or Revit applications.

How to open:

It is unlikely that this file type is mean to be opened directly by the user.

How to convert:

Various license files are not meant to be converted to anything else. However, a lot of programs can actually print the license from the "About" menu.