There are multiple ways to get the Lan Core source code.
In ZIP format, you can download it from SourceForge.net.
Also, the Lan Core source code can be obtained either by downloading a source archive (browsing the code), or by using a Subversion (source control) client.
To get the Lan Core source code via subversion you must to follow the next instruction set:
svn checkout https://lancore.svn.sf.net/svnroot/lancore
To compile the source code in Windows you will need the next develop environment.
Also, if you want to create or modify the Thin Client Operating System you will need the next external sources.