A new installer has been made available in June 2021 which no longer requires players to unpack their TDU2 installation. See this video from Alex:
Please also note their are other community server projects besides TDU World. To date they have not yet published any setup guides here on turboduck but they are welcome to do so.
The previous method (February 2021) follows bellow unedited for posterity.
Here is a quick and dirty setup guide for TDU World, which enables online free-roam in Test Drive Unlimited 2.
How to install
You must purchase a legitimate license for Test Drive Unlimited 2 (PC). Pirated copies will not work. The TDU World server checks if many profiles are using the same TDU2 key. UPDATE: TDU World have changed their stance on this due to the lack of supply of genuine TDU2 keys and the proliferation of online stores reselling the same keys to multiple customers.
1. Install Test Drive Unlimited 2. If you run the original TDU2 'UpLauncher', it will fail to connect to the TDU2 servers. They have not been running for many years. It is recommended to install the game in a location other than \Program Files\. For example, C:\Games\TDU2
2. Download and install the latest official 'DLC' patch, version build 034.
In future, this step might not be required if the TDU World launches hosts this update.
Optional: If you wish to install other vehicle mods, you may wish to 'Unpack' your game at this point. If you only wish to play online with official vehicles, you can skip this step, or return to it later.
4. Download and install TDU World. Carefully select your game installation location and verify the path is correct before continuing. The installer will connect to the Internet and download the latest version of TDU World game files.
5. Navigate to your Documents folder. Look for the folder 'Eden Games\Test Drive Unlimited 2\savegame'. If it exists, rename the 'savegame' folder to 'savegame-old' as a back up. You will need to create a new online profile to work with the TDU World servers. The TDU World multiplayer server will not support your old friends list used with the official TDU2 servers from 2011. If you do not find this folder, you can skip this step.
6. Go to the TDU World website and create an account. Take note of the username and password used here - you will enter the same details in game later. Check your email and spam folder to complete the activation process.
7. On the TDU World website, you will see your username, date joined, and an empty list of profiles. When you create a new online profile in-game, it will be listed here.
8. Optional, but recommended to avoid crashing to desktop. If you are using a 64-bit version of Windows (most are), download this '4GB Patcher', extract, and run it. Select the game executable to patch (i.e. C:\Games\TDU2\testdrive2.exe) and complete the patching process.
9. Go to the folder where TDU2 is installed (i.e. C:\Games\TDU2). Find 'UpLauncher.exe' and create a Desktop Shortcut for it.
10. For players with the Steam version of the game - go to the folder where TDU2 is installed and check if you have a file named 'key.txt'. If you do not, create the file and enter your unique serial number for the game in the format XXXX-XXXX-XXXX-XXXX
Please note that shared serial numbers are checked by the community server and banned from logging in.
10. Connect to the administration web portal for your Internet router and open up the required ports in its firewall, and forward them to your gaming PC's IP Address. (A static IP address may be required). UDP 8889 is especially important.
11. Launch Test Drive Unlimited 2. (UpLauncher.exe). The launcher should now display TDU World. Click Play. At the title screen, enter any Nickname (shown to other in-game players) as well as the username and password you created on the TDU World website. If you are prompted by Windows Firewall, 'Allow' the game to access the Internet.
12. Complete the tutorial sequences before attempting to look for other players. There are known issues where some players cannot join other players which are being looked at.