Depends how that's coded (I didn't look) but in general a liberal and intelligent application of GetLocalPlayer() in conjunction with the duplication of a lot of this code (or making multiple instances if it's vJASS) could make it work for all players. That's likely a significant amount of work.
You might be able to, instead, allow multiple players to use that interface, but only ever 1 at a time. So if player 2 is using it, player 1 cannot. That would probably be simpler.