There would appear to be a contradiction between section 2.0, and the above COPYRIGHT.images statement, although I am not sure. I have never really understood just how graphics files, which are free standing components, are covered by the GPL.
By "free-standing", do you mean that the graphics file is not a part of the Postilion executable? I think that's what you mean, though I cannot be sure. If that's true, arguably there is no contradiction between the GPL and the distribution terms terms for the graphics. After all, many GPL-covered programs read and display text files that have different distribution terms. So I think it is ok to choose the distribution terms on the graphics separately. However, there is a serious problem with distribution terms that say, "You can use this only together with FOO." They don't allow people to reuse parts of one program in another. He felt that he had worked hard to create a group of icons which gave Postilion its own feel, and that he would be upset to see these images combined with other images, or used in another program, without his consent. Since people are free to add other images to Postilion, that can o combination could happen anyway. Also, it is hard to distinguish between "another program" and "a modified version of Postilion." How much change does it take before it becomes a different program? That is a tricky question, because a large enough change in Postilion could change it into something that *appears* completely different. For example, suppose I delete all but one subroutine, and add the whole code of GNU Emacs. I could say I have modified Postilion, but the result would more typically be described as a modified version of GNU Emacs, with one subroutine from Postilion added. Both descriptions are valid. So can I use those graphics in this combination of Postilion and Emacs? Maybe yes, if you think of this as a modified version of Postilion. No, if you think of this as a modified version of GNU Emacs. So how much change in Postilion makes it forbidden to use these graphics? The current terms don't even try to answer that. It is certainly possible to change the terms to state some sort of answer, but I don't think that any answer will make sense. And unless this is extremely restrictive, it will permit things that would make Marco unhappy. I think that the right thing to do is to stop trying to prevent use of the graphics in "different programs".