Back to your question -- The interface stuff, IIRC, is there not only to
support the 3-axis joystick from the gameport, but also to power their
'protection' scheme dongle, which uses the annunciator line, etc. in
conjunction with a software check. I _think_ the power line is just to run
the light, but it may be to power the resister pack in the dongle.
Many years ago I tired of that setup and just patched the code so that it
was no longer required, both for the CAD 1+ package and for the CAD 2
package. If you'd like the details, let me know. It makes these runnable
without that blasted dongle on any computer that would otherwise support it.
For example, I use CAD 1+ on a IIGS (the 'plot' portion of the package - I
have many legacy drawings).