As long as it’s non profit, it counts as volunteer work. Even better if it’s independent and not within a club, but still great if within a club. I doubt they would ever verify, but on the common app, you’re given space to explain the activity, so you can just explain how you started doing it in that space.
And thank you! He would certainly be interesting for you to talk about in your “why Columbia?” essay and how he has shaped your own interest and dreams for the school.