I'm running Zap on shared hosting. Some people run it on raspis. It uses the Unlicense and is reasonably feature rich without being overwhelming and has evolved for over a decade. Our focus is on a Facebook-like rather than Twitter-like experience with ethics, permissions, and privacy. It's on the LAMP stack which some people hate but a good carpenter never blames his tools. It's not the most lightweight server available but gives you a good balance of features and performance. Anyway, that's the pitch. There's no shortage of projects in this space and most have a lot better marketeers so nobody is going to be heart-broken if you choose something else.
One of the things you'll discover about fediverse developers is that every developer of another project (and all the users of that project) think developers of every other project are scum so you kind of have to do your own research.
Thank you for your time.