From the menu.
Libraries\Schematic Symbols. HIghlight the root and select "Show Subfolder contents", Select All, Archive browse for location and save.
That will create a .CSA ASCII archive file.
If your other CAD package can import that then job done.
You can do the same with the PCB library to create a .CPA ASCII file.
These are the only ASCII type files that you will be able to create with CADSTAR, Zuken's own format but still importable by most other packages.