Clips would get Gallo in a 3-team sign-and-trade using the 2018 1st round pick they got from Houston to move Jamal Crawford's salary to Atlanta, while Paul Millsap would be technically traded to Denver instead of signing outright with the Nuggets.
Atlanta would be expected to buy out or trade Crawford so that he can land with a contender and haunt the Clippers.
But seriously, I don't fully understand this deal from the Clippers' standpoint. When they let CP3 go to Houston, I could buy the theory that Jerry West had advised Ballmer that his team wasn't going anywhere and needed to blow it up. But then re-signing Griffin and signing Gallinari and thinking they can compete with the Warriors seems like the type of ill-advised moves that would be totally uncharacteristic of Jerry West.