I "think" it started with Illustrator 10. It's the oldest guide I've found, plus it reads...
Welcome to scripting, arguably the most exciting new feature of Illustrator. No other
feature, new or old, can save you as much time, effort, and money as scripting.
About this manual
This manual provides an introduction to scripting Adobe Illustrator 10 on Mac OS and
Windows. We realize that not every Illustrator user will be familiar with programming
terms, concepts, and techniques, so we’ve included Chapter 2, “Scripting Basics,” which
contains introductory information that should help get you started with scripting. If you’re
an experienced AppleScript scripter or Visual Basic programmer, you will probably want
to skip to Chapter 3 to get the specifics on scripting Illustrator.
...aside from this book that mentions Illustrators 9 supporting AppleScript