This article needs to make up its mind about which VisiCalc is "original". The 1979 Apple II one, or the 1981 IBM PC one.
There can only be one "original".
There can only be one "original".
"The original VisiCalc program that ran on the IBM PC in 1981 still runs on today's PCs."
You are misparsing the sentence, applying “original“ as a modifier to the wrong phrase (“VisiCalc program“ and not “VisiCalc program that ran on the IBM PC”.)
It's a parse that many readers will make.
Knowing that it's not the right parse requires background information.
Consider "The original Yacc that ran on Version 3 Unix in 1975". Here, background information steers us toward that same parse; we don't think about there having being some previous Yacc.
What also steers the reader toward that parse is that it's the opening sentence of an article. So there is no contrasting frame established such as that different versions of VisiCalc are being compared. The topic seems to be VisiCalc, whatever that is, and evidently the original one ran on the IBM PC in 1981. That's the message.
If something is described as original in the opening sentence, then it looks like the meaning is the main one of "original": unprecedented, new, not derived from anything else. Not like "don't forget your original document in the photocopier".