The glossary format used now is not extensible. It's flat HTML that just doesn't work when it comes to having things added to it. We need something else, maybe RDF-based or somesuch, that is extensible. Currently, the glossary wouldn't work well cross-app because it has Firefox-specific stuff in it, so we need to do this so we can have a Firefox glossary file and a Help on Help glossary. Otherwise, Thunderbird Help will contain quite a bit of irrelevant information...
This may seem strange, but using XUL might be a good idea because you can have XUL overlays. Just thought I'd throw that out. Even though the help content pack can inherit RDF files, mozilla won't do it by default outside of trees (although don't quote me on this since I've been gone from mozilla long and haven't kept track of recent API additions).
Morphing some; Help on Help should never need the glossary, as if it did need it there would be a problem with the Help on Help text. The glossary should be a per-app thing. For the fix, we just need to move the glossary XHTML file into the app location and change the jar.mn entries for it. This is simpler than some complex glossary entry merging process, and because Help packs can't coexist at the same time anyways, I don't think it introduces any conflicts.
(In reply to comment #2) > just need to move the glossary XHTML file ...and the RDF file for it, too.
Targetting bugs which were targetted to Firefox1.1 before the move to mozilla1.8beta2.
Fixed by file moves in bug 289555.