In response to this post, I received news from Bill Trench that he is in the process of finding an on-line home to make his book source files available. If anyone would like to offer his source a home, or provide advice on effective ways to do this, please get in touch with him.
On a side note, I'd like to get some information on this site about free options for on-line book source hosting and distribution. Options like github exist, but I have limited experience with them. If someone is willing to write a post let me know. Such information would be of great use to the community.