from the link: "using 30-year-old or older machines."
from the fine article: "First released in 1981; discontinued in 1994 using 30-year-old or older machines."
I recently (three weekends ago) fired up my Commodore PET 2001 (a *genuine* pre-1980 computer) and have been writing a Forth for it. It's really a lot of fun, and I'm finding that 30 years experience in various high-level languages has improved my "6502 assembler golf" game a lot. It's very incomplete, but the inner interpreter mostly works. Feel free to throw down on it here
Real programmers don't comment their code. It was hard to write, it should be hard to understand.