It invented numerous features including overlays, later to develop into DLL’s.
Unfortunately this is not a selling point for many word processor customers. :)
I guess the lesson is copy protection is bad, but it’s also bad to depend on a tangled mess of code that can only be maintained by a single hero programmer.
Noted author William F. Buckley (whose politics I completely disagree with, but I see his intelligence) was an avid WordStar user. He’d have technically-minded friends go to great lengths to get WordStar working on increasingly incompatible newer hardware and operating systems.
He said of WordStar, “I’m told there are better programs, but I’m also told there are better alphabets.”
Wordstar (for DOS) was the first word processor I used a lot - I loved the keybindings, which were very common in other DOS applications of the day (like Borland’s Turbo-* products). It’s interesting to read the history - I didn’t realise it was already in decline by the time I started using it in the late 80s.