[SQLite]

Minor correction: SQLite is not closed to contributions. It just has an unusually high bar to accepting contributions. The project does not commonly accept pull requests from random passers-by on the internet. But SQLite does accept outside contributed code from time to time. Key gates include that paperwork is in place to verify that the contributed code is in the public domain and that the code meets certain high quality standards.

[Zigurd]

I was about to try to make this point: there have always been projects that attract more potential contributors than there are competent contributors.

And there have always been techniques for identifying quality contributions from new contributors.

[xnorswap]

Thank you for the correction, I should have said "not open contribution" rather than "closed contribution".