A mere eight months after its release, it seems that the JACK Audio Connection Kit - an app that enables you to connect the audio and MIDI ports of your music making apps together - may have bit a development brick wall. Developer Crudebyte has confirmed that it doesn't work in iOS 7, and is unlikely ever to do so.
The problem is said to stem from a new policy that Apple introduced with iOS 7 that prohibits any Inter-Process Communication among third-party apps. We're not sure why this means that Audiobus works but JACK doesn't, but it seems that the additional features that JACK provides beyond straight 'audio sharing' are the ones that are causing the problem.
You can find out more on the Crudebyte website, where the developer summarises its position by saying: "It is unlikely that JACK will ever work again on iOS 7 upwards, simply because it is not in our hands and we consider it unlikely that Apple will move in its position regarding this new policy/OS restriction. In case you want to continue using JACK on iOS, then you should not update your device to iOS 7 or later. Keep in mind that you cannot downgrade your iOS version once you updated it."