Here you can see an overview of projects I am involved in. Why I am interested in open-source projects is mainly the motivation to grow personally.
But here are some other points what open-source means:
Great way to learn how to code.
It’s fun, it should be a hobby.
You can give something back.
First Moodle contribution
Moodle lives from contributions, but the main core is mainly maintained by Moodle HQ. For all interested people, on this page (https://moodle.org/dev/contributions.php?version=x.x.x) you can see all developers that have ever contributed to this gorgeous project.