The executable jar file is given at
Download Source Code
The software is version controlled using a Subversion (SVN) repository. Source code is located at
The URL above provides also the the download command (using subversion). In the subversion repository, theres is a "trunk" and "branches". The "trunk" contains the main development and should always at least compilable and executable. "branches" are copies of the "trunk" for temporary modifications (see the subversion homepage) and should not be downloaded.
Downloading requires a subversion client or an appropriate plug-in for your IDE.