There are several ways you can get TSPSG source code.
TSPSG source is available at SourceForge.net git repository. To get the latest version of the source you need to make a clone of it1:
git clone https://github.com/leppa/tspsg.git tspsg
The tspsg directory with the latest available source will be created. This needs to be done only once.
If you already cloned the repository and want to update the source in tspsg directory to the latest version, run from this directory:
git pull
You can browse TSPSG source code with your web browser. Just follow this link:
http://tspsg.info/goto/git
The source code for all TSPSG releases is available in ZIP and TAR.BZ2 formats. You can download it here:
http://tspsg.info/goto/downloads