Framing a recruiter asking for a github link as a question of contributing to the tech world is disingenuous.

Stack overflow, Google, Apple, etc have contributed significantly more to the tech world than 99% of open source projects. Ruling out developers from closed source projects is myopic.

The one that is built on titanic effort of others not all of which was compensated in any way at all?

This is how open source works. Either you are cool with giving away code without compensation that others will use or you aren't. You can't have it both ways.

I say all of this as a huge open source advocate btw.