The project should have a README explaining how this is a C implementation, how to get started with it, and note, at least for now, the road map to full feature support for the PV8 SDK.
C has a lot of different styles and opinions on style in the world. Document standards so that others may contribute without a considerable number of styles creeping in.
Currently we use ints to reference colors, sprites, fonts etc. This should be changed to be unsigned shorts with a preprocessor configurable typedef. Using ints takes up 4 bytes, which is more than the 3 byte colors themselves. A 32 bit address also supports more addresses than is reasonable for this application. An unsigned byte is too short as we may want to support more than 256 colors. With all this in mind, unsigned shorts seems the best choice.
The current Lua bindings are done by hand, and may not be done properly. Explore the correct way to implement this and find or build a generator that will create the bindings provided the function signatures.