phpFreeChat is developed on github since March 2011.
To clone it, uses this little command:
git clone git://github.com/kerphi/phpfreechat.git
Don't hesitate to fork it, to push your contribution on your branch and to submit a pull request to the project. Your code will then be reviewed before being integrated to the official source code.
Here is more detailed documentation on how git can be used with phpfreechat: