This is client of Mr.Paint, 茶绘君, located at http://mrspaint.com
For server side of Mr.Paint, check out https://github.com/liuyanghejerry/painttyServer
Code of painttyWidget is under LGPLv2.
More details can be found at LICENSE and COPYING