If you are interested in playtesting the newest development status of the game, then you can get instructions how to do so here.
First you need to know the repositories on github:
The game repository:
This contains the newest development status.
The best solution would be to clone this repository with git, as you don't need to download the whole thing again every time there is an update and updates are quite often.
The other solution is to click "download zip" on the github page, but switch to the development branch first ( https://github.com/Duion/Uebergame/tree/development ) as only this contains the newest changes, the master branch only contains the stable releases.
When you have cloned or downloaded the game folder you will need the latest compiled executables, you can download the latest version of the full game and then copy the executables from that into your cloned/downloaded repository, then you can launch it.
Find other people to play on our Mumble or IRC.
In case you want to compile the engine yourself use my Torque3D repo branch: https://github.com/Duion/Torque3D/tree/ueberengine-dev
and use this compile instructions: http://wiki.torque3d.org/coder:compiling-in-linux