Download both .dsk & .nib images from

https://archive.org/download/Uncracked4am

Let's start with the .nib image.
A standard ProDOS disk with "bad" block #7.
We don't get fooled (again), say to DOS to ignore the checksum
and voilą the block reveals its data: a copyright notice.

Block #7 is the one and only block used by the file LMS.DAT

Now how can we tell to the ProDOS to generate an error when
reading a file? Easy! Clear all access flags attribute.

Switch to the .dsk image and use the ProDOS exerciser or if
you are reading this note in the XXI century do it with CyderPress.

I'm a notorius pedantic so in the uploaded image the block #7
a.k.a. file LMS.DAT contain the original copyright notice.

Notes

- Splash screen (C) 1993, block #7 (C) 1991 ???

- I don't intend to offend anyone but I must say that this is
  the most idiotic copy protection I have found till now