Except with clothing, the entire point is that branding is the ONLY way to protect it, you can't (well you can in the EU, but NOT effectively: and most don't even try) protect it with copyright. I restate
this link.
There is a lot of evidence - from this and many other projects like Creative Commons - that the good of society is not being protected by IP-as-practised. I can also go on at length (but you probably don't want me to) about the Open Gaming Licence and how it's changed the RPG market for the better.