Freebbble!

Freebie! Mobile App Sketch UI + Pixate Prototype is a free UI design resource made by Dribbble user Peter Finlan. As far as I can tell, its license is Unknown.

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.