Negativland are interviewed, and, not surprisingly have interesting things to say.
In the end, we came up with a sampling license that was saying, in effect, “You can reuse bits and pieces of our work for profit. You can sell it. But we’d like it if you mention where your sources come from.” And the only exception to this is that advertising can’t use it. It’s okay for anyone to use anything, except in advertising, because we don’t consider advertising to be free speech. It’s paid speech. And as artful as advertising can be, it is not art.