Confusion on your part regarding what the other commenter's complaint is. The complaint is that the source code archive they downloaded did not contain the source code. It contained an old copy of a shareware notice instructing the reader to write to Dunfield for access to the source.
Confusion on Dunfield's part: specifically, the belief that he had included the correct version of RINGSW.C when republishing this stuff to celebrate his retirement.
Finally, confusion on the part of the other commenter here, involving an assumption that Dunfield's oversight was a deliberate decision.
The author seems quite aware of this. He calls it out specifically: it's for learning and curiosity purposes.