Are there any Good Open API for Web Frontend Paint Tools?

I'm currently attempting to develop an HTML5/JavaScript application which is similar to: http://mugtug.com/sketchpad/

The source is right there, but I think I'd run into some copyright issues by cutting/pa开发者_StackOverflowsting (I suppose I could contact them), but I'd rather use some free APIs that would have similar functionality.

Thanks for the help!

Thy this-

http://caimansys.com/painter/

Another one I like is SumoPaint but, that's not an opensource

http://www.sumopaint.com/home/