A few days ago I started to work on setting up a Minetest server. Minetest is an infinite-world block sandbox game similar to Minecraft. However Minetest is free and open source software released under the LGPL 2.1 license and is under active development. If you like MMO games you will certainly enjoy this game too.
The new server is called "Yggdrasil" after the immense world tree in Norse cosmology. I think the name blends in quite nicely with the already existing "Einherjer" fps servers and their target audience of Player-versus-Player". Though in this case the goal is to focus on the environment and collaborative work to build new structures and buildings and discover new ways of shaping the world. Thus "Yggdrasil" is strictly a "Player-versus-Environment (PvE)"-server.
I am currently experimenting with different server options and it will certainly take a while until I have got accustomed to the game. I intend to add more Debian supported mods later. I hope everybody will enjoy Minetest. Have fun.