I know that the new version of the app (the silver logo version) has a paid and unpaid version. The difference is the number of pages - the unpaid version allows for one page and 2 sub-pages (I think), and the paid version is unlimited. I don't know for sure if the Mobile G version is the same way, but if it is, that might explain why you're getting that message - the project you're trying to use has more pages than the free version supports.
Also, the version of the app being used in the program is referenced in the program that's running in the processor. So the app versions aren't interchangeable once the program is loaded into the processor - you need to use the right app for the program.
I noticed the bad ratings for the app as well, but you really have to look at it in context: the app is really a utility used by Crestron programmers to put an interface that **they must make** onto an iPad. Crestron doesn't make the interface and Crestron isn't an AV installer, so the bad ratings are really sort of misguided complaints that were likely meant for the crappy dealer that didn't know how to use it.
Also, the 'not supported' thing likely means that Crestron isn't doing anymore updates to the app, but it's still available and works in particular situations. I have a customer who is still using it, and we did put it on a newer iPad when HIS ancient one died. So it will run on there, although as I'm digging through my old brain cells I seem to remember that we did have to do something to make the older project work again...it was a project re-compile in VT-Pro, I think. Nothing difficult.
Another thing to keep in mind is that you might have already paid for the full version years ago using a different iTunes account. If you're looking for the app while logged in with a different account, the app won't show up as having been purchased. Or the installer might have used their account, for some reason. Just another thing to consider.
Sorry for rambling a bit - I didn't have my coffee this morning so I just kind spit all that out in a somewhat disorganized fashion... Hope that helps a little!