Hmmm great question... what I meant by "build other things" is that you can create your own maps and other images by combining the existing tiles as long as you don't change the art of original hexes (and that's where the "no derivatives" comes in).
I considered each tile as individual images... so, if you assemble the hexes you're not creating modifications (at least that was what I was aiming) but let me know if that's not the proper CC.
If you have any further question, let me know. Hope I made it clear.