NOTE: You register in the game itself, not the website.
The installer requires the latest Microsoft .NET Framework Applications. Download .NET Framework 4 in Microsoft Download Center
A snapshot of the source code for both the client and the server can be found here:
The client and server source can also be downloaded independently here:
If you encounter any kind of problem it is recommended to post it in the Help Forums, if the same problem hasn't already been submitted. The Chat may also provide an alternative for the more common issues.