I play SubSpace (a MMO spaceship game released in the 90s) to this day. It was shut down soon after release.

The original server binaries were left on the original CDROM by a programmer.

Then PriitK, a creator of Kazaa and then Skype and Joost!, went on to re-create the client due to cheating/hacking, naming it Continuum.

Years later the server is reimplemented as A Small Subspace Server (ASSS), making it a complete fan remake of the original game (sans graphics). This is also when we finally got server side mods, everything before that was client only or a hack.

We even got on Stream Greenlight.

https://store.steampowered.com/app/352700/Subspace_Continuum...