Considering that XCode uses a version of clang (which is open source) for it's compiling, I wouldn't say that the main compiler is proprietary either. I think t

Considering that XCode uses a version of clang (which is open source) for it's compiling, I wouldn't say that the main compiler is proprietary either. I think that what people mean is that all of the "usefulness" of Objective-C comes from using it with OSX/iOS development, and all the stuff related to that is proprietary.