Pure Tween is a really small and clean implementations of Robert Penner's easing functions.
It just contains a Tween static class with many interpolation functions, a TweenTest script that generates curve images of these functions based on Unity.TestFramework, and some pictures have already been generated.
It is fully open source, free and well designed.There is no strange API, no extra integration, no unuseful codes.It is pure.
You can do anything you want with it (just legal things).