This question, http://space.stackexchange.com/questions/17353/nasa-cfs-core-flight-system-http-prn-to-29shn5w-turns-open-source, while perhaps too broad and perhaps not well written, was in my opinion closed far too early.
Flight software is a huge component of the cost of a new space vehicle. cFS has the potential to be a huge game changer in how we write flight software. Open source (e.g., Linux, Python, numpy/scipy, NetCDF, OpenCL, OpenGL, OpenVDB, Blender, CMake, VTK, ...) has drastically changed how software (and scientific software) is written and used. cFS is one of the shining lights in NASA's late entry into the open source game.
Just sayin'.