Also shout-out to https://glitch.com/ which puts particular emphasis around community and learning. I use it anytime I'm preparing code for a class, workshop, demo, or open source documentation.
He co-founded a game company Ludocorp in 2002 to create "Game Neverending", then pivoted its photo sharing functionality to become Flickr and sold it to Yahoo in 2005.
He then co-founded another game company Tiny Speck in 2009 to create "Glitch", and in 2013 spun out the chat tool the team built while making Glitch to become Slack, which IPO'd in 2019.
(Funny enough, one HN commenter sort of called it happening again[0])
I believe Stewart gave (or sold?) the Glitch.com domain to Fog Creek in 2018[1] and the game's site lives on at a new domain [2]. Some discussion from (Fog Creek's) Glitch's launch about the domain name change at [3]
[0]: https://news.ycombinator.com/item?id=1111863
[1]: https://twitter.com/anildash/status/841345310655950848
i imagine there are businesses which facilitate these types of transactions