The Solar System and World of Near game texts are licensed with the Creative Commons Attribution license. (There is some layout, art and such in the books that’s unlicensed.) What this means in practice is that anybody can use the licensed materials pretty much any way they want, provided they attribute the source and act in good taste. The idea and encouragement for doing this comes from Clinton R. Nixon, who licensed the original Shadow of Yesterday with the same license. I thought it only fair to continue the license, when most of the material in my booklet spins directly from his work.
What I’d like to see in practice is others claiming the opportunity to work with the Solar System, too. You could use it as the rules-set for a campaign setting, for example. I don’t know that it’s a very good idea to force a setting into a given rules-set (I’m thinking of all the horrible d20 books we’ve seen), but if Solar System fits perfectly for something you’ve been meaning to do, or you’ve developed something interesting for Solar System in conjunction to play, then hey, go nuts.
The logo to the left here (or something like that, anyway) is what we’re planning to use, insofar as there is need for a brand label for the Solar System. If anybody wants to do a Solar System product of some sort and wants to use the logo, feel free to contact me for vector files (and other support too, of course – if nothing else, I can help out with proofing your new game mechanics and such).
The above holds for the new World of Near book as well: Its text is CC licensed and I welcome anybody to continue from there to whatever direction they’d like. The logo here is likewise available for anybody wanting to reference the brand in their own work.