Dragonbones is a free editor and a runtime that allows you to use skeleton animation in your games.

The runtime has a free license and has no fees, compared to the alternatives.

official website
http://dragonbones.com/en/index.html

js runtime
https://github.com/DragonBones/DragonBonesJS

online demos
https://github.com/DragonBones/Demos
https://dragonbones.github.io/demo/EyeTracking/index.html