Chances are still pretty low, however. I used to be a long-time open source maintainer, and I definitely found (based on my own experience, and the experience of others trying to get started on projects I've worked on) that the barrier to entry to almost any non-trivial code base is fairly high. And debugging is usually more difficult than adding a new feature.

Open source communities also don't "just happen". It's pretty rare for someone to throw some code in a GitHub responsibility, wander off, and later find that it's suddenly become actively (or even passively) maintained.

Unless it's an app that's mission-critical to my life and there aren't any alternatives (even if they're not as good), I can't see myself digging in to fix bugs. And even then, it still feels like a hard sell.

I also feel like most apps that people might love enough to even consider diving into also have server components. If the company running the service shuts down, that's another barrier to setting up your own (assuming the backend pieces were even open sourced too!).

Sure, it happens, but those tend to be very very exceptional cases.