Here is my answer to all the questions from the Introduction post.
My name is Ondřej Čertík and I am doing my PhD in Chemical Physics at University of Nevada, Reno. For my work, I need C/C++ libraries (like PETSc and Trilinos) as well as Fortran libraries (BLAS, LAPACK, ARPACK and some FEM packages). My own code used to be in C++, but last year I switched to Fortran (so I need Fortran as the first class citizen). I then wrap it using Cython and call it from Python.
I took Sage, and rewrote the build system in Python, and created Qsnake (the core is BSD licensed, other packages have their own license). The packages are hosted at github, and it uses a json file with package dependencies. Quite a few people have tried it already and here is our plan with the package management. I need a lot of packages, I would call it engineering packages, mainly around the SciPy stack, and a few more numeric packages.
I don't think there is any fundamental problem with my approach, it works great for me and does exactly what I need. Obviously more improvements would be cool, see the packages plan, and I work on it as my time allows.
My key insight is that it is a lot of work to get things working and testing on various platforms (Linux, Mac so far). Also it is advantageous to keep packages compatible with Sage, because then people can reuse them and instead of creating yet another fork, I view Qsnake as a complement to Sage.
The way forward that I can see is to simply continue working on Qsnake (in my case), or if I can see significant progress on some competing product, I might join it. I am working on Qsnake. I don't have much money to spend on it, but thanks to being compatible with Sage, there is possibility of common workshop with Sage (I got the offer from William Stein to organize such a thing, but I am currently too busy). I use Qsnake almost daily for my own work, and I improve it as time permits. I don't have much time in general though, but I do my best.
Finally, I think that the most important insight that I have learned is that it is important to get and discuss good design and so on, but it is even more important to simply start working on something and make it fix a problem for somebody (me in my case). Qsnake does exactly that, and as I said, I am open to adjust it's goal if anyone wants to join, as well as join any competing project, if somebody else think he can do (and does) a better job (which shouldn't be that difficult given my own time constrains). In the meantime, I simply continue with Qsnake.