At least one of the reasons I had not yet tried updating the ledgersmb package to the 1.5.x series is that the dojo package currently in Debian Unstable is only 1.11.0 and I had thought that the 1.5.x series needed 1.12.2 like the master branch did. However, the dojo requirements for the LedgerSMB application were recently updated and while the master branch went from 1.12.2 to 1.13.0, the 1.5 branch only went from 1.10.8 to 1.10.9, according to the commit comment.
I'd kinda been making assumptions about the dojo being used in in the1.4.x series as well, it seems; althought that has worked, at least in-so-far as being able to log in. Now that I actually have an idea where the dojo information is kept in a dojo install (dojo/_base/kernal.js), I checked and found that it seems that it is only dojo 1.9.1 that it has been being used with the LedgerSMB 1.4.x series. On the other hand, it's also true that the 1.4.x series doesn't use dojo as much as the 1.5.x series do.
What will help with all this will be actually getting autopkgtest implemented for ledgersmb as much as possible, as in the case of the ledgersmb package it will allow running application testing using package as it is actually installed. And since I now know how to get a proper origin archive for a specific dojo version, I'll be able to test against those also instead of just those versions that are in the main Debian package repositories. And, better yet, be able to compare how it tests with both the version it was release against as well as the version actually in Debian.
If there's nothing else barring it, perhaps I should get the ledgersmb package updated to the 1.5.x series while the dojo in sid is still only 1.11.0? But should I wait until I have it working with autopkgtest? That I haven't decided yet.