Applying Stallmans free software philosophy to creative works
One of the key motivating factors for free software is so that a user or interested third party can see how a program works, how it was created, verify it for bugs and security, and can easily modify it including to fix bugs. To some degree this philosophy can be carried across to other works covered by copyright, yet the Creative Commons licenses don’t yet offer a license for this. For instance, say I do a drawing with a pencil on paper. There isn’t really any source, only a binary (the final drawing). If you want to change it, all you can do is draw over the top of it or use an eraser (just like modifying binary encoded machine code).
However, works covered by copyright are no longer solely creative, and no longer a single final binary. Just like software code which although could have creative thought put into it, it is mostly functional. I have the same thought process for creative works, I want to be able to see how it was created, and how I can modify it. Take for instance a digital painting, where every brush stroke is stored as a brushstroke. This way a third party could come along later, select the single brush stroke in question, select it and change the paint color.