I ask this not as a gotcha, it’s a serious question.

There is no way to write an app that doesn’t use a single piece of Apple code.

Create a new project in Xcode, simply write print(“Hello, world!) right click on the print method, click “Jump to Definition” and you get to read Apple’s code.

To say nothing of all the boilerplate stuff (and more importantly all the stuff underneath it that is automatically created when you create a new project and that is necessary to run the app.

The open source SDK you talk about might be completely free of Apple’s code, but it most definitely makes use of Apple’s code.