Not safe and not comfortable to my eye.
The convercycle looks pretty cool i guess ... but how much does all that hardware weigh? I think i'd prefer one of those Bakfiets cargo haulers with seats in front if I was hauling kids (scared a trailer would get hit--plus I could lean forward and hit the kids if they started acting up.) But o0nce kids hit a certain age, hauling them isn't so much an option---riding with them might work, though. A tow-along, then a tandem if it is one kid ... two kids, no luck. As for cargo ... I can haul a huge amount of cargo on a bike with good racks---I have hauled a good part of a drum set once (not particularly safely.) No need to buy a complicated, heavy convertible. Add to that the fact that for hauling goods a trailer is fine (You can hit my rice, it doesn't mean as much) ... but if the guy can sell his bikes, good for him, I guess.
A bicycle is one of those simple, effective machines which simply don't lend themselves to a lot of fancy modifications. The basic stuff works so well, it is hard to improve. Just my opinion.
EDIT: Also when I look a the picture of the guy riding as a passenger----the guy in back has no lateral support, not much back support, and is all hunched up. I wouldn't want to ride in that thing for more than a few minutes, and only if I knew the rider was Really stable. I certainly wouldn't feel safe putting a child in there. Again, just one person's opinion.