The last paragraph of the article says, "For whatever it’s worth, fiendish subscribers must adhere to at least one limitation: They must wait 30 minutes before ordering another coffee."
Yes, there is that limit –– and a good one. You could get around it maybe if you were with some friends doing a klatsch with staggered drinking rates and drink start times, but then you'd just look really cheap.
you could just ask for an empty cup and split the drink with a friend. then a little bit later, get another one. During a long talk with a friend, you could continue to do that and go through several cups. I don't think a random barista who makes 10 bucks an hour will care, especially if you leave a tip. The owner probably won't care because he makes more money every time you get a cup of coffee.