Download and use at your own risk. Despite the public release, Valve has warned all potential users that they should be very familiar with Linux functions before using the early software. Otherwise, they suggest waiting until late 2014 for a more stable version.
Alongside the OS release, 300 people will be very happy to learn via email that they have been accepted to recieve Steambox prototypes to use; with a very exclusive Steam badge as well. No word yet on if TF2 hats are involved.