I wouldn't assume that anything except what is in the downloads section is up for grabs.
Obviously, I can't speak for Chris, but I know that some of his Kickstarter project maps had customized versions made for high-level backers that they then made available for free download to other backers. I've lost track of which those are...
Of the stuff in the map gallery - a couple are from his commercial products (his copyright).
Of the rest of those, a couple are WotC produced maps, and all of them denote copyright by WotC and/or Lucas.
Resolution is 72dpi (low) for most except Taris and Ossus
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(For reference, the files he makes available to backers are 300dpi)
You could contact him about the YT-1300. It can't hurt to ask.