Does this count as volunteer work? (Contributing to open-source software projects)

I contributed about 5000 lines of code to an open-source software project called Appium. It took me about 200 hours. Would this count as volunteer work? I didn’t have to physically go anywhere as one can contribute from any computer connected to the internet. Also, how do I include this on my Common App? Should I just list it under the “activities” section as volunteer work?

My biggest concern is that I don’t know how I would prove that I did this. The software is open-source and anyone can see the source code. However, I don’t see how I would prove that I contributed 5000 lines… Would appreciate some guidance on that too.

You don’t really have to prove anything, adcoms will trust you. I think it’s more of an extracurricular activity rather than volunteer work.