Yeah, I'm a bit confused. To me the big news doesn't seem to be that some mathematicians wrote a book using Github.
The is that there is now an expansive, informal/readable, and machine verified writeup of homotopy type theory.
To be fair, this is a community of mostly non-mathematicians, most of whom will probably have no use for this work. But yeah, certainly that's the real "big deal" here.
Well, homotopy type theory is in the same general area of study as the type theory studied in computer science.
I just told the department librarian to buy a copy, even though I don't do category theory, so you're not alone :)