Building on other sketches licensed under CC-BY-SA
Originally posted on the
Sketchpad blog 
Excerpt:
Unless otherwise specified by their author(s), works built on Sketchpad are distributed under the Creative Commons Attribution-ShareAlike 3.0 Unported license. This means that Sketchpad sketches can be cloned and modified by others, both on Sketchpad and elsewhere. This also means that sketches can build on other CC-BY works, such as those built using other wonderful Processing websites, such as SketchPatch and OpenProcessing.