From what I have seen, and having bought the upgrade myself, the 'January Software Upgrade' is not tied to a specify account regarding the ability to sync the applications to a device.
As long as the .ipa file is located in either of these directories:
~/Program Files/iTunes/Mobile Applications/
~/Library/iTunes/Mobile Applications/
Then itunes will sync the upgrade to whatever device is plugged in, as long as you are signed in on the iTunes account you bought the upgrade with.
R-Fly