Yeah, I usually don't push with it because I know that most people using GitHub really mean well in terms of software freedom, but I personally avoid GitHub (not just uploading things to it, but downloading them from it if there's an alternative) because of that reason. And I agree, if it's about standard language, we're talking about C. It's veeeery far from perfect, but it's the only language that can be called a standard.
The points I mentioned, of course, are not a matter of "what's right". I don't think there's one right way. Those points are details about what I feel that we, the members of the Stunts online community, generally would like to have.
Like Dreadnaut said, to really reproduce the behaviour, you need to fully interpret the code. I think it is possible to create from scratch a physics set that's convincingly close, without being compatible, but just how close is something we won't be able to know until we really try hard to do it. And in all honestly, I don't know if it takes less time to comprehensively reverse engineer the physics engine of Stunts or to develop a convincingly close brand new one. I don't know it.
Hiring people... I agree that'd be a great push and probably would also make us want to participate as well... and I don't think we here are not willing to pay. I personally would be happy to contribute. My only fear is that maybe the person(s) won't do it the way we would like or maybe we end up paying and not obtaining what we want. Also, while there are many skilled programmers, I wonder how many are skilled in software based, low level graphics and physics... The few I know about are here in this forum or have been here.