I started hacking on g++, the GNU C++ compiler, because I was using SGI machines in my first job and the boss was too tight to pay for enough compiler licences!

It was the early days of the internet and I got exposed to some genuine next-level devs. In particular, I went to a conference and spend two days with Linux developers, and I knew that these were the people I wanted to work with. So I started hacking on a side-project I'd begun, which became ipchains, and next thing I know I'm being paid to write Free Software! Had no idea that would last for over 25 years...