I was glad to see this page about groff, which is much underrated as a publishing system. The perl script for replacing some markdown markup with chosen groff macros is very interesting. I was however wondering about why the OA chose to write their own macro set rather than simply using the mom macros? Was it simply the need for German markup (and I take the point that languages other than English is an issue)?

Nils Holm (https://www.t3x.org/) also publishes ebooks using groff, but he does not (so far as I am aware) publish his markup or macros.

As to the writing: I'm still working on the sentences, so 45 pages is a distant goal.