HRS,
I asked the Branson folks about biodiesel and they sent me a very nice disclaimer.
With that said, Kukje, the manufacturer of Branson (and the engine) also make Cummins small diesel engines (press release March 2002). Cummins seems to have engines in just about every big truck on the road, and more and more fleets are using biodiesel blends. February 1, 2005 John Deere came out in support of biodiesel.
Even the American Society of Testing and Materials (ASTM) issued Specification D 6751 for biodiesel. With all that said, I feel the risk of using biodiesel in a new machine really carries a small risk for me.
It is true about older fuel delivery systems, just as other folks have posted, that the natural rubber seals and hoses will soften and degrade with biodiesel. The new engines all use synthetic rubber componants.
Paul