> en.wikipedia.org/wiki/Dia
This really depends on your definition of dialog management. I’m not aware of any engine that can follow and maintain conversations over a long period of time. However, I thinkBruce Wilcox‘ ChatScript engine is probably what you’re looking for. It has won theLoebner Prize Turing test quite a few times, including again in 2015 (for details seebrilligunderstanding.com)
See also the list of dialog system APIs listed under my Quora question: