[jrockway]

As an upstream maintainer, I prefer that people contribute rather than maintain their own forks. It just makes it easier for other users; what if they want a feature that's in user A's repository and a feature that's in user B's repository? It's not their job to figure out how to merge them: I do that so they can focus on adding features instead.

But with that in mind, there are plenty of cases where you do need to maintain a proprietary fork: testing new ideas, integrating with internal infrastructure, and so on. This is certainly more difficult than letting someone else maintain the project, but less difficult than being the maintainer yourself. You basically miss out on big refactorings, but it's no different than being a regular user of a library that makes incompatible API changes.