WordNet.Net is held in a Subversion repository, so to retrieve the source you need to install Subversion, and optionally a Subversion GUI client.  For those already familiar with Subversion, you can use any means you are already familiar with to checkout the source.

For people unfamiliar with subversion, and if you are using Windows, the easiest method is to use Subversion coupled with TortoiseSVN.

Firstly, download and install the latest version of Subversion from this link: Subversion Installer

Next, download and install the latest version of TortoiseSVN from this link: TortoiseSVN Installer

Once you have installed Subversion and TortoiseSVN follow the procedure in the screen recording below to retrieve the latest sourcecode: