"the best of those, Zoom, is doing very well"

Is Zoom really the best? No other comparable platform out there?

Anyone know how difficult it would be to build something like it on top of aws or a similar cloud?

I've been playing around with jitsi (https://jitsi.org/) and have been impressed. I may play around with deploying their server on aws this weekend (via this docker, most likely: https://github.com/jitsi/docker-jitsi-meet)