Paul Buchheit was core developer of gmail , who left gmail in 2006 - where its become shitty afterwards. He founded friendfeed and then got acquired by Facebook - and he left facebook to become angel investor / he is also main Partner of YC . he invested in many great startups like Twitch . On the opensource part , he build tornado web framework which is really important async framework for python ecosystem. Jupyter is built on top of tornado . He is active in HackerNews .