I posted earlier about finding the software & Arduino source code.
As to the hardware - there's a lot of hardware info in the Files sections. People posted photos and info on their builds of PHSNA and some people altered it as they saw fit into different configurations. There's also info on Return Loss Bridges, power calibration circuits, a measurement receiver, a crystal test fixture, methods of calculating frequency compensation parameters, examples of measurements made using PHSNA and so on.
So yes, there's a confusing mass of good info in the Files section.
And as I said earlier, Jim N5IB designed a lot of variations on the basic board set. None are really obsolete, they just allow using different hardware.
The power detector board with its AD8307 log power chip has remained mostly the same. The sandwich board of main board, Arduino board and DDS board has many variations.
But I didn't intend to describe all of that here. I just want to point to a PDF that Jim did that does a pretty good job of sorting out all this info. It's at the top level of the Files section, and I found it on page 4 (items 61-68) of the Files section. The file is called PHSNA_FAQ_Sheet.PDF.
It explains a lot of the hardware variations, tells what is meant by Type I and Type II DDS modules and answers many questions. It even points to where to find the software which I described in my previous email.
So I'd recommend starting with that file.