I agree that this is not session music but I don't think that this book originally had Orange associations. It has tunes in it like The Home Rule Jig, The Land League, The Wearin' of the Green, and Brian Boru's March. And the next major Irish Warpipe publication, "McCullough's Irish Warpipe Tutor & Tune Book" (Belfast and Dublin: 1924/6) was published by an Irish Nationalist. The Cork Volunteers had a Warpipe Band around 1914-16, and the Gaelic League promoted the 2-drone Piob Mor. http://www.scottishtartans.org/irish_kilts.htm mentions IRA pipe band competitions. See Dave Gallagher's site, http://st.louis.irish.tripod.com/irishwarpipe/index.html for some interesting reading and lots of photos of Irish warpipe bands, including in both World Wars -- Definitely not Orange: http://st.louis.irish.tripod.com/irishwarpipe/id3.html, The Pope and the Warpipes.

Another interesting thing about the Walsh book is that the tunes are written with varied key signatures. This leads me to think that the author expected some players of the Brian Boru pipes (patented 1908) to use the collection.