I didn't make that github repo, I don't know who did. But it's old. The most recent archive on makerlisp.com is from a few days ago. Go there if you want the most recent stuff.
This is a snapshot of the source preview I put up just before my trip to the Bay Area Lisp & Scheme Users Group in February, before I had shipped any products. Apparently someone was just trying to help me get more exposure. I have no problem with this, the attributions and links are all correct and it is a proper snapshot. As a reading / demonstration example, to get the feel of the system, this is fine. But I update the archive on my website every few days, and that's where you can find the latest version.
There's an archive posted on the Download page of makerlisp.com with all the source and lots of examples. And you can run the code on x86/Linux to get a feel for the system.
In general, start from makerlisp.com to get all the info that I've made available. I have nothing on github.