What's the rationale? Who are the target users? I go to the site and I have no idea what exactly this does that's better than the alternatives. It sounds like its trying to do everything.
The target users are academics who collaboratively use mathematical software like SageMath (http://sagemath.org), Octave, Cython, R, IPython, etc., in their teaching and research, but don't want to have to wrestle with installation problems and coordination with collaborators (say via Git). Numerically, most users are students taking courses from such academics. I started the project because I was teaching courses on SageMath, Cython, and LaTeX to students, and the installation burden for the students was a major problem. Also, I was frustrated by how difficult SageMath is for people to install on their own computers... even after 8 years of development (it only seems to get harder over the years, not easier!).
This may be less interesting to you, but SMC seems like an ideal platform for data-science and software related job interviews. A few years ago I interviewed with Enthought. We used Google Docs for the real time coding!
Thanks for suggesting that. I think SMC could in fact work well for those applications, though I don't have any real insight into them or know how to get into those markets myself.