Quantum Fog, my old Mac application for doing calculations with quantum Bayesian networks, is now open-source (it’s finally out of the closet). Check it out at GitHub.
Quantum Fog was originally written in C++, but we plan to rewrite most of it in Python
By the way, I highly recommend the GitHub website if you need to collaborate with a group of people on the writing of a computer app or a website or an arXiv paper, or many other possibilities. I use GitHub in conjunction with a Windows app called TortoiseGit, which I also love and highly recommend.