While I was able to find a wxPython source browser I was not able to find any checkout option for the source code.
Note, I tried svn co http://svn.wxwidgets.org/svn/wxPython/branches/WX_2_8_BRANCH but it requiest an account, something I do not have.
You have some info here.
For anonymous (read-only) access, you can checkout wxWidgets from SVN with the following command:
For example, to checkout the WX_2_8_BRANCH, use the following command: