It doesn't help when people muddy the water by using the wrong terms - a fair number of freebies say they are Public Domain when it is clear, from the rest of the readme, that the author is in fact reserving copyright but allowing free use, and possibly even modified redistribution subject to limits. Others stick in a claim to Trademark status, which doesn't apply both because it takes active effort to obtain which they haven't made and because Trademark wouldn't be relevant if they did.