I’m not an IP Attorney but I’m pretty sure there is not copyright protections for design or clothing. US Copyright excludes copyright for anything having a utilitarian design that exceeds mere expression. Copyright protects ideas not functionality. The hat doesn’t seem to fall into any area of copyright protection because although it has a distinctive color, the design is secondary to its use to actually keep you warm. It also has no separable qualities or elements that would distinguish the hat from being anything more than a hat. Nothing about it is “pictorial, graphic, or sculptural” which are all copyrightable. I’m sure the license is a stronger claim, but it seems like they could still sell the hat so long as they didn’t clearly identify it as a Firefly hat. Just name it, “ugly orange hat” and the sale should be legal. Even vague references to Firefly, like Browncoat hat or Jayne’s hat should be sufficient (assuming those aren’t trademarked or licensed terms, which they may be). Oh well. I guess it’s in the nature of large corporations to over threaten legal action regardless of the existence of a valid claim.