You aren't following me. 'Learnable Progamming' is 'built on' Khan Academy in that it is a response to it and it works from the JavaScript/Processing environment that Khan Academy put out. There are obviously questionable assumptions being made about it being a good environment in the first place, but it is simply used to make a point. Zed makes some straw man arguments by conflating these concepts.
From what I remember, Bret originally said some things about teaching programming with this visual interactive stuff, resig&khan academy went and actually implemented something, saying that it was inspired by Bret and then Bret wrote his big post saying that what resig & khan academy did wasn't quite what we had in mind.
When I saw the talk I understood it as more of "resig implemented the interactive paradigm" then "resig implemented the things in learnable programming"