I’m surprised hardly anyone else has mentioned Wesnoth yet. I last played it over a decade ago, so I’m not sure if it’s still as well-known now as it used to be, but it’s one of the highest-quality open-source games out there.
It’s a turn-based fantasy strategy game that feels like a combination of Advance Wars, Fire Emblem, and D&D. And I suppose it was a lot more unique back in the 2000’s when there weren’t a dozen indie games out there that fit the same description.
I was wondering the same thing, I wanted to add JSON Feed support to an app I’m writing but couldn’t find any examples of it in the wild, and Google was no help. Good to know that NPR has one, though.