www.ycombinator.com/nonprofits/
The question of whether open-source producing non-profits fit into YC is still a good one. I couldn't find an info on whether they have already accepted such non-profits, but the incubator Fast Forward has:
> Intelehealth built an open-source intelligence engine for assessing primary care conditions
https://qz.com/792685/silicon-valley-wants-to-save-the-world...
(Obviously, a clone itself wouldn't suffice, you'd need to start with federated identity, and....)
https://www.crunchbase.com/organization/diaspora#/entity
It didn't work out so well, mostly because a.) actually cloning Facebook is pretty hard and b.) users don't seem to want to switch to fully-open Facebook or Twitter clones.
I'm making a strong bet that people do want to switch to fully-open social clones, because it's hard for me to imagine citizens of 2024 or 2028 conducting an effective political system using today's monolithic social technology. But the current ecosystem sucks for it.