Wikipedia:Don't confuse trademarks with copyrights
 | This is an essay. It contains the advice or opinions of one or more Wikipedia contributors. This page is not an encyclopedia article, nor is it one of Wikipedia's policies or guidelines, as it has not been thoroughly vetted by the community. Some essays represent widespread norms; others only represent minority viewpoints. |
 | This page in a nutshell: Trademarked images are not non-free, unless they are non-free. |
Simply put, trademarks are used to protect use of a name or other identifying mark in relation to a product, service, or any other entity. Copyright exists to let authors have the exclusive right to their creation for a limited time period.
While something may be protected by both (say, a logo or something), many logos just aren't protected under copyright laws. While Trademark law kind of fills this void, that does not make it non-free. Internal consensus states that the Definition of Free Cultural Works only deals with copyright related restrictions.
Trademark law is a completely different subject to deal with, but it is out of the scope of what can be defined as free content. Sure, you can use Wikipedia content legally for your own encyclopedia, but you cannot use our Wikipedia logo or specifically use the name Wikipedia to brand it on the front cover, because the name Wikipedia and the Wikipedia logo are registered trademarks.