How can I get the source code for X-Quiz module

Hi,
How can I get the source code for X-Quiz module…!
I have an issue::
For the quiz questions, I want to disable multi-select for the answers, and for that I need to edit the source code. Whenever I try to edit it, only text edit option is available and the source code is not being showed up. Can anyone give a solution for this ?

The sources are in the download, see http://extensions.xwiki.org/xwiki/bin/view/Extension/XQuiz/ (the XAR file contains wiki pages that you import in your wiki and which contain the application code).