There's opensource Obj-C compilers by both GNU and LLVM/Clang available for windows and linux, so it doesn't have to be hosted on apple hardware afaik, but when

There's opensource Obj-C compilers by both GNU and LLVM/Clang available for windows and linux, so it doesn't have to be hosted on apple hardware afaik, but when you start using library frameworks, that I'm not sure about.