JoelSpolsky's FogCreek software span off a bunch of interesting products and companies including FogBugz and StackOverflow / StackExchange

Now they've created a SocialCoding platform called Glitch

FogCreek becomes Glitch : https://medium.com/make-better-software/fog-creek-is-now-glitch-8d0308aaf69e

Is run by AnilDash

Now does "React" and other serious JavaScript applications :

https://glitch.com/create-project