this works for win 7 im not sure about other OS.
So you need to have the latest version of vorpx then in the game make sure its display settings are set to direct x mode with window mode enabled and in vorpx just make sure the check box (disable aero on game start) is NOT checked. Also have DK2 set to extended mode as the secondary display. you might want to also change the key binding for edge peek mode in vorpx settings.
(edge peek is what you will use when you are in the menu screens so you can interact with them)
Then when you run xstoryplayer with vorpx running it will still start on main screen but to move it to your rift all you have to do is hit window key + shift + arrow key left or right depending on how you have your displays set up. and there you go xstoryplayer 3.0 on oculus rift dk2
The only thing is vorp x is not free i bought it a while ago to play non vr games in vr it does not officially support xstoryplayer but i decided give it a try and im glad i did
here is the website if your interested
http://www.vorpx.com/