Geneshift is nearing completion and will be available for purchase on Steam very soon. Until then you can follow and wishlist Geneshift on Steam so you're notified when it's released.
Running ./Geneshift will open the client and running ./GeneshiftServer will autostart the dedicated server. Note that this is a demo and is mostly used for the dedicated server. You can purchase Geneshift on Linux through Steam. Here are some options you can set for the dedicated server:
-m maxplayers Sets the max number of players.
-p port Sets the port to host the server on.
-h hostname Set your username here to earn community credits while hosting.