I have the impression that a Riparium is its own style of aquarium aquascaping. From the things I have seen, the idea (or ideology) is to form an emergent state of plant growth that appears to form without a land mass (almost floating if you will). This forms an underbellly of shaded water mass that provides an artistic impression.
Now, looking at Tom's first pic of the driftwood and plants emergent on top, could this be a riparium style?? I say yes. It still provides for the open underbelly of water column, provides an emergent state of growth and plant mass, while limiting the actually land mass composition to below the water line (no, I don't consider wood as land mass).
I think you need to look outside the box and see that there is a true distinction between a Viv and a Rip in an aquarium. One is an attempt to match an actual ecosystem, one is an artistic style - similar to an iwagumi and its attempt to match a landscape or impression of something in real life other than an underwater reality.
Nothing we really do in a wet box is true to nature. The minute we filter the water, or add some type of outside chemical, lets face it, we have altered reality. Impression, I believe, is what counts.
Rips are just another impression that has evolved and I truly believe they are all distinctive albeit, I can see that there can be cross overs and hybrids with a Viv.
Just my two cents.