I started building an open source private blogging system[1] when my first kid was born, and it eventually evolved into the skeleton of a social network--but fully decentralized using RSS and self- (or paid-) hosting. I concluded the only way for a network to actually avoid selling out was for there to be nothing to sell. If I give away the software, and don't control the network then there is no need for users to trust me. It continues to be an interesting journey as a side-project (not raising money means I'm still working a day-job).
[1]: https://havenweb.org