This discussion was specifically for the Python function bge.logic.LibLoad(), not a general interface for async lib loading, I’m sorry if I didn’t make that clear. That’s not to say a logic brick couldn’t be added latter, but I was looking for feedback on a Python API, which means I’m not really concerned how it affects non-Python users. Also, Python callbacks are already used by the BGE in the form of KX_Scene.pre_draw and KX_Scene.post_draw. KX_Scene.post_draw is the only way I do HUDs these days.
As for an example of getting progress via a callback, look at post #3.
I agree with that moguri, the focus is the Python binding.
pre_draw and post_draw are the callbacks I was looking for. As far as I remember the purpose of this callbacks are rendering purposes rather than logic.