Just made the source code of SCS, a space-sim game I’m working on, public. The game is in early prototyping phase, but has some basic features already implemented. It uses a custom rendering engine based on OpenGL, also included in the repository linked above.
Game and engine are written in C++11 with heavy use of the Standard Library. Some Lua code is also used for configuration.
Currently, the project is only building for Mac, so if you have a Mac, feel free to give it a try
Also requires a modern video card with OpenGL 3+ to run.