I believe those books are all there...so far, no problems.

I have already downloaded the PDF files of several of them, and am working my way thru the list to see which ones I want.

When I first looked at this project a few months ago, I wondered if I should offer them MY copy of -

"The Popular Songs of Scotland with Their Appropriate Melodies", by George Farquhar Graham, 1887.
...but I see that they have added it, also.
(It was listed as one of F.J. Childs' sources)
This is one of the largest and most complete books of Scottish song, and it does have tunes included.

The whole resource is amazing.