[fsloth]

I think you are a bit confused. I would compare Mathematica to a an old digital desktop calculator. Nobody who used those wanted to see their insides. The point in Mathematica is not that they have some closed source pixie dust that no one else can understand or implement. The value of the software comes from the fact that you need a lot of grunt work in a large software package to maintain user experience - fix all the unfun bugs etc - and very few open source projects manage to attract enough interest to have people do also the gruntwork and not the interesting new development or 'cool refactorings'.