The idea for SQLite actually came out of his frustrations with an existing database called Informix that was installed on a literal battleship

they said, “Well, do you have any pricing information?” “Well, look, I tell you what, let’s have a call tomorrow and I’ll get back to you on that.”
Of course, inside, I was like, “What? You can make money with open source software? How does this work? How do I price this? I have no idea how to do this.”

Somehow or another, and I don’t know how this happened, Mitchell Baker, she’s the woman who runs the Mozilla Foundation, she got wind of this and called me up, says, “Richard, you’re doing this all wrong. Let me tell you how to set up a consortium.” She laid down the law, says, “Look, the developers have to be in control. Their decision is final. No voting rights on what gets to go into it. The companies that are using, they get the honor of contributing money, but you make all the decisions.” She was very adamant about this and she laid out everything. She’s a lawyer.

I actually started following some of their processes, and one of the key things that they push is, they want 100% MCDC test coverage.
That’s modified condition decision coverage of the code. Your tests have to cause each branch operation in the resulting binary code to be taken and to fall through at least once.

I looked at Git, I looked at Mercurial, and I looked at my requirements and I thought, “You know what? I’m just going to write my own,” so I wrote my own version control system (fossil), which is now a project unto itself, and that worked out very, very well

Source : https://sebsauvage.net/links/