An Apple ID is indeed free. I've had an Apple ID for downloading Xcode for years now. At the moment the only way to get an app signing key is by purchasing a $9

An Apple ID is indeed free. I've had an Apple ID for downloading Xcode for years now. At the moment the only way to get an app signing key is by purchasing a $99 license (which also gets you publishing privileges in the App Store) but it is extremely likely that in the future getting a signing key will be completely free and will not require a $99 license fee. It won't get you App Store submittal and won't get you publishing on the App Store, but I think that is fair.