Sketch Freebie! Land.io UI Kit + Landing Page!
Sketch Freebie! Land.io UI Kit + Landing Page! is a free Template design resource made by Dribbble user Peter Finlan. As far as I can tell, its license is Creative Commons Attribution 4.0 International.
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.