I posted this comment elsewhere:

For some background about World Bicycle Relief and the original “Buffalo Bike”, see this video by Berm Peak on Nebula (also YouTube).

As for the 2-chainz design, I think it’s fairly brilliant, as a way to avoid a delicate derailleur, which MTBers will know is vulnerable on terrain due to being low-slung. This sort of thinking also highlights how engineering and design make tradeoffs, since the weight penalty of an extra chain is not important when the ultimate objective is a rugged, durable bicycle.