All GUIs should have the source posted, to make sure it isn't malicious. However, could it be possible to use applications offline, downloading recent block chains from a separate computer and transferring them to that? It wouldn't be possible to make transactions I assume but you could view received transactions, right?
This is just a GUI for the daemons, so it would depend on the daemon allowing you to do it. You can transfer the whole data folder, but I suspect you're talking about individual transactions and I don't think they support that.
I'll look into it though.