I found out about this unique back to back through my friend Martin on YouTube. This tandem was built by Jan Friedl (on the captain's seat) and Jirka Hebeda, both from Czech Republic.
Jirka provided the following information about the bike:
The design and frame were mostly done by my friend who is piloting it in that picture (with the rest of his family on board). The basic idea is this: a cross between racing and touring configuration easily converted between the two.
The frame was designed to be simple yet effective and tolerant to manufacturing imperfections. Front geometry is done so that the head tube and main frame tube are perpendicular - for easy building.
The rear end is designed to be stiff under load of baggage. The ride is rather harder as a result of the sporty configuration, but still quite ok. It is reasonably fast and we did beat Martin's tandem in that 24 hour race :-). The wheelbase is 2300mm (about 7.5 feet) and front wheel trail 70mm. Seats are movable in large range via several holes in the main frame and clamp on the seat stays. Pedals are mounted by a bracket onto the main tube and can be adjusted finely to the millimeter.
What's intriguing about this bike is it's apparent simplicity. I can't see any curved tubing, only angles. If Jan and Jirka are willing to share the plans, I'd like to try to build one of these.