I thought about the Objaction encoding, in that case your "original" work is the changes in the figure, and the encoding is the method to insure that downloaders are only getting your original work (as they have to already have the starting point), so I think it fits O.K., without spelling that out. I also think it is more important to present a concept - you can only give away YOUR work as Freestuff - than get bogged down in 500 rules that sombody is going to find a way around anyway! ;-)