Without an apple ID you can compile an iOS app, but can only run it in an iPhone Simulator on a Mac.
With a free apple ID (no additional registration needed) you can also install your compiled iOS app on your iPhone and have it working for 7 days before you need to re-install it.
With a free apple ID (no additional registration needed) you can also install your compiled iOS app on your iPhone and have it working for 7 days before you need to re-install it.