I think he's trying to sell a locked product which adds some overhead whenever you "fork" the data into more formats. Not knowing enough about how Garmin protects their electronic data I can't really say how to go about that. It sounds like the intention is having a locked down flash card similar to how Garmin sells some of their map data.
The ultimate protection would be your own proprietary format encrypted and an Android or iOS app that can only read it.
TBH a lot of the trails in the Guidebooks are already online in some form or another that can be converted (with GPSBabel) into whatever you like. I really like the books and will continue to buy them for trips as things to do. They are really well done. The electronic routes or waypoints as I can build myself or find them somewhere online. With Google Earth/Maps and a converter it is also much easier to share this data with others.
Here is Dusy-Ershim trail after finding the GPX online, opening into Google Earth, removing unwanted bits and saving as KML. Then I imported with Google Maps and can share to nearly anyone I want. Further, if you have Mac/Win browser Google has the Google Earth viewer working within Google Maps so you can use the 3D fly-over style navigation to follow the route.
Dusy Ershim - Google Maps