The code base is freely available under GPLv3.
The assets are also provided, but they remain proprietary; also some BGM songs could not be published due to restrictive license issues. But there is everything you need to recompile the game for Android, PC or Web. Feel free to play with it!
For more details about the internals of Exp3D, you can refer to a previous post I wrote on the topic.
On a side note, the WebGL demo has also been updated to work better on mobile screens, with a responsive design and support for touch events.