They are very awkward instructions. I have yet to use it, so I can't comment on the quality of it. Arturo pushes a build and a diff for each PR(attaches to the link on the orange/red/green dots). This is a start of Arturo and I would love it to be Open Source and Developer friendly, focusing more on the Books + Code aspect.
It does build all the versions of the document on each push, which I find makes it a bit slower for frequent check-in.
The diff idea is interesting as a value add, especially - I project - for per-diff discussion or so.
In any case, this was not a disparagement. At this point, the more of these ideas we have, the better it is. I just wanted to point out that at least some of the functionality was already implemented somewhere else.
And you can setup a commit hook to trigger the preview build automatically.
Given that common base, I am curious what the specific other difference are. Especially to justify paying for a private repo account.