This discussion probably happens a lot of times. IMHO the project being opens, doesn't means that every little piece of it needs to be open. Fedora is not the only example, ask about Firefox (iceweasel case) [1], or even the Ubuntu logo [2]. Graphical elements are delicate, and since there are detailed instructions to use it [3], I think there is no reaons for create flames about not being open, or is less free for that.
Finally, there are legals about trademarks [4] that everyone should read. This doesn't mean that you can't collaborate, just that some things are more delicate than others.
Br,