Richard Schneeman has been contributing to open source for over a decade, and he's in the top 50 contributors to Ruby on Rails, a popular web framework. He helps maintain a few open source projects, including the Puma webserver and the Ruby Buildpack for Heroku (his day job). He's got 1.6 billion open source library downloads and has seen firsthand: how open source projects work, what needs they have, and how anyone with an interest and some guidance can make an impact.
In addition to his personal contributions, he wrote a service, CodeTriage, that has helped thousands of developers start and sustain open source contributions. He has mentored developers through their first contributions at his workplace. He has taught dozens of students how to program including his tenure at the University of Texas as an Adjunct Professor.