iOS 7 Icon Kit (for Photoshop and Sketch)
Actual license text is as follows: “These are free to use, but please do not distribute them! I’d love it if you linked back here if you use them anywhere! Enjoy!”
Helpful hint: Dribbble users are nice. If the license is unknown, it is usually because they forgot to mention it explicitly; not because they were being stingy. Ask nicely and they will probably allow you to use it.