FPLBase is the lowest level game library we use at FPL taking care of input, rendering, and resource loading (shaders, textures, meshes etc.). It also offers useful functionality for dealing with Android input devices and HMDs, and threaded resource loading.
FPLBase is not meant to be an "engine", in that it doesn't dictate anything about how your game is structured. It is meant to shorten the distance between an empty project and "drawing stuff on screen", by providing the typical minimal functionality you don't get if you work on top of raw OpenGL. More Info »
It is also not meant to be a platform abstraction library (like SDL, GLFW, Glut etc). We actually use SDL underneath for that purpose.
Other FPL libraries can be used on top of FPLBase, for example FlatUI can provide font rendering and game UIs.
FPLBase is available as open source from GitHub under the Apache license, v2 (see LICENSE.txt).