Think of "code" as an instructional data set used to guide the operation of a machine. A "copy" is not really the issue. Instead, the machine operation is the issue, and that sort of thing has always been considered to be eligible for a "design patent".
Not looking up the decision at the moment I believe they used the word "patent", and not simply "design patent".
Remember, though, I'm not a patent attorney ~ just worked with a couple of them for 20 years in my 4 decade long career.
Their lunchtime lectures were always quite illuminating. Made the bizarre seem unbelievable.