Immediately after your payment is processed, you will receive an email with an access link. You will then be able to download all of the following DRM-free distributions:

The price also includes downloads of all future updates, a free Steam key at launch, and a lifetime account on the main game server that I am running.

The source bundle includes the server software, allowing you to set up and run your own server (a web server with PHP/MySQL is required).

You can take a look at the system requirements.