Actually the entire premise of MIT OCW was to make superior educational material available worldwide i.e to a mass audience, and it was a pretty big deal when announced. After OCW, several other organizations started doing the same. I wouldnt be surprised if Sal got his inspiration from OCW. (The Univ. of Tubengin TIMMS predates OCW but is completely unknown). So imo OCW has the larger impact.

Also, I've been following KA for a while and its definitely been around a lot longer than a few months, its form has changed a couple of times, much improved now. IIRC Sal originally started by posting on youtube.