From it's conception, Photonic3D has supported multiple screens on all operating systems that support the concept. However, we've also built support specifically for Raspberry Pi's multiple HDMI screens. This is because the Raspberry Pi doesn't yet support multiple screens through the natural XWindows facility of the underlying OS.
Using these new screens are pretty straightforward. Simply choose: `Raspberry Pi Force TV` → Use the DSI port on the Raspberry Pi. or `Raspberry Pi Main LCD` → Use the HDMI port on the Raspberry Pi(known in XWindows as :0.0).