Joe Watkins has an excellent (and potentially scary) read here on how some major aspects of the PHP project might depend on just a few people. He asks how many people does the PHP project depend on — and he says the answer is just two:
Maybe as few as two people would have to wake up this morning and decide they want to do something different with their lives in order for the PHP project to lack the expertise and resources to move it forward in its current form, and at current pace.
I'm wondering what the “bus factor” is for some elements of WordPress core! 🚍
I cannot think of any critical items that would come down to just two people, but it's certainly possible if a few people moved on or disappeared there would be some impact on the project. The question of “what if one of these people was Matt Mullenweg” has also been thrown around in hallway conversations.
Andrew Woods has a follow-up article based on Joe's post focused on how to attract developers to PHP core.