I was looking for a dead on feature for feature exact replica including look and feel. You are 100% correct there are some excellent tools and libraries that duplicate most (all?) of the features. But I was playing around with the idea of what it would take for a perfect replica (for science of course). Turns out it's really hard even if you jump start it with those libraries and an existing reference implementation.

That was the point of my comment... Robust commercial software is hard.