Windows and Mac OS X binaries will be hosted here from now on. The download links are below.
Source code is made available for Linux users to compile the graphical user interface, or for all users who wish to develop using the API.
Please note that compiling the GUI requires g++ and Qt 5. These might be available in your repository using something like
sudo apt-get install gcc qt5-qmake qtbase5-dev
Depending on your Linux version, you may also need to install the following:
sudo apt-get install mesa-common-dev libglu1-mesa-dev
From within the /gui directory, run qmake and make to compile.