Wrote an article
In one of my previous role, decades ago, I was part of a team that needs to support Applications running under NCR UNIX SVr4, I had to undergo company sponsored trainings of UNIX SVr4 End-User and Administration. That was my initial introduction to UNIX. And not having the immediate source code of UNIX available on the server opened my eyes to look elsewhere. Enter linux or GNU/Linux, depends on who you're talking to, and my view of Operating System and software in general was never the same since.

I immediately fell in love with 'Open source' and 'Free Software'. Linux pushed me to using most of what I learned from UNIX SVr4 trainings. The learning curve of switching from UNIX to Linux was almost painless. Back then, and still up to now, when you have a question about linux and its userspace applications, just 'go to the source'. This means reading the source code which can be installed on the host, if not yet already. In the succeeding years, I also learned about FreeBSD and the availability of its source codes. Learning is so much fun if you have both the running application and the source code from where it came from. In those days, tldp.org and slashdot.org were some of my favorite sites. Nowadays I pass some of my free time at github.com specifically on SerenityOS repo