This is the second release (v1.0) of the Rain rig, a free high-quality rig created by the Blender Animation Studio team. You can learn more about the character design and creation process in the Stylized Character Workflow course by Julien Kaspar.

The rig is free to use, provided that the you respect the CC-BY license and include the credit: Rain Rig © Blender Foundation | cloud.blender.org