All of the modules and examples in the Decker source repo and homepage are available under the MIT license. Any non-code assets for which the MIT license cannot be logically applied should be understood as available under the CC0.
I also formally extend the same to WigglyPaint and all of its components. If you're interested in making something wigglypaint-like, you should be sure to check out WigglyKit, a collection of contraptions that are specifically designed as more modular/reusable versions of the components in WigglyPaint.
Hope that helps!