Regarding the topic, I can easily imagine a legitimate app on Google Play with available source code, where you find something inconvenient and your attempts to suggest a fix to the developer did not lead to the desired outcome. Currently, you or your developer friend can simply fork such an app, fix the issue, and release it for the general public without any extra paperwork. This Google policy would make such a developer suspicious/disabled by default (if the developer is not already verified), unless proved otherwise.