Kaplan worked together with Craig Barnes, and in the words of Barnes: "I did the bulk of the programming although Julio also did a lot and from time to time we added other people."
https://www.schach-computer.info/wik...arnes%2C_Craig

Delta-1 is an unlicensed modification of Boris rev 1, as found out by bataais: https://www.schachcomputer.info/foru...ead.php?t=6034

And I think Sandy/Morphy is based on Sargon? Maybe Steinitz is too.