You're wrong on both counts. I mentioned MirageOS in the other thread, in fact. MirageOS merely links in the minimum portion of the operating system required to support a particular application. I still would not consider that to be 'the app running the operating system'; i.e., if you examine the application's call stack (with a kernel debugger and OS symbols) at any point in time, there's still going to be a lot of 'OS' stuff below the main entry point to the application.