I built a few in the past, typically with a friend or two, but they were dying together with the initial hype/interest.

So, lately I tried to focus on bigger challenges and set up companies to handle the os project. My passion is security which I think should be more open. Cryptography is pretty much open nowadays (meaning everything we use crypto-related is likely open), but many other areas in security are not, e.g. authentication.

First project SoloKeys: https://github.com/solokeys/solo

An open source security key, FIDO2 certified, open hardware and firmware. Profitable, revenue selling the hardware + kickstarter campaigns.

Second (newer) project Saasfrom: https://github.com/saasform/saasform

A modern auth system for SaaS, with teams & payments. Revenue will come from cloud solution. Just started, onboarding the first beta customers.