Project Mu is mostly about getting the messy parts of the UEFI ecosystem sorted out: Instead of hoping that IBVs ("Independent BIOS Vendors") clean up their act (because, to be frank, they don't), they get ready-to-use components that Microsoft is using itself on the Surface products and provide a certain baseline standard (security, UX, ...).

The difficult part about firmware in general (hardware initialization) is still under lock and wrap though: you'll have to get it from the silicon vendors and link it with the open EDK2/Tianocore (which is the UEFI base) and Mu (which is a toolset to extend that base) components to a full firmware image. In particular, those components aren't distributed as part of EDK2 or Mu.