It's not that Resolume flips the image. It's that DirectShow does not recognise that it needs to be flipped.
The need for flipping is quite common with capture devices, and most capture cards send a flag with the signal that it needs to be flipped. Of course Datapath's own software recognises this flag correctly, but DirectShow doesn't.
You'll probably be happy to hear that Res 5 will have the same native support for Datapath as it does for Blackmagic. Aside from less latency, that also means we can handle this sort of stuff ourselves.