I made an inquiry to the Ribbet crew as to whether I'd be allowed to use Ribbet's components commercially. They replied that Ribbet can be used commercially, but not all of their clip-art (such as that epic phoenix decal in the pictured cover) and fonts are necessarily free for commercial use, because they got them from other sources.
That means, if I were to eventually publish The Phoenix over there, and I wanted to use that cover, I'd have to do my research and determine whether or not the font and that graphic are free for my intended use. (And I don't even remember where I got that stone tablet from! Inevitably, I can't use that cover, but my example is purely theoretical.)
So now I'm going to ask: does anyone know any good resources to get amazing, eye-catching fonts at little to no monetary cost? If you know of any, please share them in the comments. :)