Most open and standards-compliant format for a JSON news feed

I can find a huge amount of converters for Atom or RSS to JSON. I can see App.Net and a Google Feed API for pushing feeds in JSON which seem to have traction. What I am struggling to figure out is what's the 'open standard' way of serving up a feed without tying people to transform XML or to use my own (or someone else's) proprietary JSON format.