It's cool that Apple's using your stuff, it's not cool they're not giving you attribution. I'd add a JGuitar url and copyright notice to all your images, so that this is displayed in Apple's results, and also call a lawyer.
The OP put something on the internet with the intention for others to use it. Apple used it. Is there anything on his site (terms,"rules") that indicate what Apple is doing is considered non-acceptable use?
Shouldn't we be happy the world can still work like this - bottom-up implementation with presumably good intentions - instead of having to talk to lawyers before every tiny step we take? We're taking about looking up a guitar chord for crying out loud.
Of course better attribution is desirable. Why not let this be Step 2.
I admit a bad turnout could be an unexpectedly high bill for the OP. And I would assume Apple to turn a deaf ear if he'd requested them to help pay that bill. But aren't those the consequences of putting up a public API?
@asaph If you want: please follow up on this and let HN know how this plays out. What course of action you took, how Apple responded (if at all)
Congrats... I guess
[Edit: typo]