Which Reddit-alternative open project should I contribute to?

As a dev with a disdain for corporations who take advantage of the position their users helped them get to, and a lot of time on my hands, I'd like to help to build an open alternative to Reddit.

But not an alternative that will inevitably end up in the same position in 10 years, so that rules out for-profit startups. This needs to be a source of information that is BS proof.

Instead of starting from zero, which existing open alternatives looks promising to you?

Some important factors for me:

* Portability of data

* Decentralized or federalized, with interop between nodes

* Fully customizable CSS or layout skins, like old.reddit

* Open API and platformability

* Plain old HTML navigation by default, no JS frontend (but the option for others to build that for themselves and others if they prefer it)