That was a long blog post to tell us that they are no longer entitled to valuable free API access. It was a mistake to think it would last. This story has been repeated so many times here. As soon as the author started making money (they conveniently excluded their sales revs), they should have negotiated a written contract for access for a fee. It could be cut of app revs or pure API charges. Also, I am sure some smart managers looked at all their free API giveaways and decided there we no longer useful to their business model.
The author disclosed his sales revenues here: https://news.ycombinator.com/item?id=41124971 . He sold 467 copies of the software after 10 years, for a total revenue of around $2000. He never exceeded 200 API calls per day. I don't think it would have been worth Yelp's time to negotiate for a percentage of that.
