What you are missing is the distribution stage. You can't install it quite like you are suggesting.
First, you need to build an installable package (from the base directory, NOT from src):
Now, you should see a target directory. If you drill down, you will find three zip files, one for springpython, one for the samples, and one for a plugin called gen-cherrypy-app. The files have a version number and timestamp embedded in them. The core framework is located in springpython-<version>-<timestamp>.tar.gz. If you unpack this file, then you will find a setup.py script embedded in them, which you can either run through:
./build.py --clean --package
python setup.py install
Now, springpython is available to whatever version of python you installed. (No promises regarding IronPython).
jython setup.py install