I can't see / understand why you would have 2 user accounts on the one Mac ..... unless it is you and someone else? I have never thought about this, but I would "guess" that the software is linked to the machine rather than the user account (as was the case with my early pc version)? I suggest that you ask Microsoft directly?
By Mike A on 19 April 2016
As far as I am aware - the renewable version costs les as its a subscription, as Office 24/7 or whatever it's called whereas Office For Mac updates (albeit infrequently). I gave up on Oulook though it doesn't work without constrict annoying pop-ups on BT with Home Hub 4 or 5.
By Wireless Voyager on 01 February 2016