They added many of the v.2 changes in Defiance and Resurgence, but not templates (as well as keeping their own reaction system). It is its own beast, but you need all the books to play. You can play version 2 rules with too much trouble using the K47 stats (we often forget the K47 difference anyway), however you probably need to keep the reaction rules as otherwise the some of the special hand-to-hand and movement rules might be a bit op.