It's taken a while, but the source code for Barren Planet has finally been released. The code can be examined and downloaded from https://github.com/cyningstan/barren. If you're familiar with git and github, you can also create forks of the project, or clone the repository for tinkering.

The source code repository contains the code for all the constituent libraries of the game: CGALIB Graphics Library, CWG, SPKLIB and KEYLIB, so you don't have to grab those separately. CWG, the Cyningstan War Game library, isn't available as a separate library yet, but it will be added to the web site (and to GitHub) soon.