We — Manton Reece and Brent Simmons — have noticed that JSON has become the developers’ choice for APIs, and that developers will often go out of their way to avoid XML. JSON is simpler to read and write, and it’s less prone to bugs.
See the spec. It’s at version 1, which may be the only version ever needed. If future versions are needed, version 1 feeds will still be valid feeds.
See Mapping RSS and Atom to JSON Feed for more on the similarities between the formats.
This website — the Markdown files and supporting resources — is up on GitHub, and you’re welcome to comment there.
We worked with a number of people on this over the course of several months. We list them, and thank them, at the bottom of the spec. But — most importantly — Craig Hockenberry spent a little time making it look pretty. :)