Eero was a fully binary- and header-compatible dialect of Objective-C, implemented with a modified version of the Apple-sponsored LLVM/clang open-source compiler. It featured a streamlined syntax, Python-like indentation, and other features that improve readability and code safety. It was inspired by languages such as Smalltalk, Python, and Ruby.
Like LLVM/clang itself, Eero is cross-platform. It has been tested (in the past, but not recently) on Debian Linux using the GNUstep runtime.