I just made my own system up Halley, sorry I didn't use any reference material.
I basically use a sprite offset for the "top" of the bone and use a hierarchy system for moving "child" sprites when the "parent" sprite is moved / rotated. It can be very simple if you don't start adding the option to scale sprites too.
My own system produces a text file containing animation data. There are already a number of C++ libraries for
Spriter and perhaps
Spine that you might find more useful. I believe the intention is to include these libraries (or our own version) in AppGameKit eventually.
this.mess = abs(sin(times#))