You can get the latest stable version of Simple Chat from the Simple Chat PPA on Launchpad.
sudo add-apt-repository ppa:impomezia/development
sudo apt-get update
sudo apt-get install schat2
sudo apt-get install schatd2 # If you want to install the server
sudo add-apt-repository ppa:impomezia/stable
sudo apt-get update
sudo apt-get install schat2
sudo apt-get install schatd2 # If you want to install the server