In the 80s I worked on BPCS, an early ERP system, and yes it was coded in RPG2, and RPG3. Mind blowingly hard to understand the source code but I credit my efforts then with later finding AWK so easy and logical. IBM had also just brought out the baby System36 which looked like a PC beige box but was actually a minified s/36 if I recall correctly. Didn't sell well. Then there was RPG for DOS which I heard of but didn't use.

If the authors client had been using an RPG accounting system for 40 years then it might be BPCS and there were tools out there to convert RPG to other less traumatic languages.

But fascinating article nonetheless and brought back memories of being an apps programmer. I also remember those dongles. Really fun when you had multiple apps with their own dongles and only one port.