xkcd-script/font/xkcd-script.ttf gives a "not a valid font file" error, and the live preview page is showing as raw HTML source for me (Win10, both Firefox and Edge). I almost gave up before discovering the tree/master/xkcd/build OTFs via a recently-closed issue; I can't see anything in the main xkcd-font README pointing at these.
Also xkcd/README.md and xkcd-script/README.md appear to be blank, although I'm not sure what if anything is supposed to be in there.