You will need to install some dependencies first:
It is already installed.
Open Terminal and install pip:
sudo easy_install pip
then using pip install pygame
sudo -H pip install pygame
Finally, download the latest version of the eduActiv8 source, unpack it somewhere by double-clicking on the downloaded *.zip file.
eSpeak (optional but useful)
You may need to install Homebrew before you can install eSpeak
ruby -e "$(curl -fsSL https://raw.github.com/Homebrew/homebrew/go/install)"
brew install espeak
Finally to run eduActiv8 from Terminal: