All information concerning the development and beta testing of
Pingus is at a separate section on this webpage (which is
currently out of order), so that players don't accidentally see
stuff that wasn't yet meant for release or grab a development
snapshot, instead of a stable binary by accident. So if you are a
player don't enter this section, but instead stay on the light
site of the Pingus webpage and simply wait for the next stable
release which will contain everything in a nice packaged and
useable form, going to the development section will just spoil you
a lot.
If you are or want to become a developer you are of course welcome
to the dark site of Pingus, there you will find source code
documentation, a todo with stuff that needs to be done and
unfinished game elements that might need you to finish them.
Short summary for those who just want the source:
svn co svn://svn.berlios.de/pingus/trunk/pingus/