Ian, are you UK?
In the US, a couple of copies available equates to many of us as a vanished species. Yes, they can be bought, once, by someone who may or may not have any way of sharing the songs. The songs vanish from the oral tradition when that happens, because not enough of the collectors are performers and not enough venues want that particular sort of song. Not a lot of cowboy singers around these parts, podhuh. *G*
No, I am not sure of the copyright situation; they were shared by a collector who said they were quite rare and I went from that point, to try to play through the first book, only to find I was risking damaging the value of his material-- collected for its memorabilia value rather than its musical value.
This seems to me to be a site where people share what they have learned or are learning, rather than wring profit from what they hold. IMO to discuss copyright at Mudcat is, at best, difficult to do credibly.