We support operating systems that not even Microsoft and Apple themselves support anymore, such as macOS X on PowerPC Macs, and RetroArch being available on Windows OSes as far back as Windows 95.
RetroArch can run on the usual platforms like Windows, Mac OS X and Linux, but it stands alone in that it can support far more platforms beyond just that. Aside from running on both Windows and Mac, this emulator comes jam-packed with a ton of features to improve.