It certainly is! Older diesels are a hell of a lot more tolerant than modern diesels, and you certainly wont have any trouble, if anything, it should prevent the usual glazing of your cylinders caused by standard diesel which is certainly a beneficial factor.
I would assume that the only reason they mention the 14 year old policy is because anyone with a vehicle of that age could technically blame the companies fuel should the engine pack in. More than likely however, is the fact that bio diesel tends to eat through rubber fuel hoses. You may want to replace your current fuel hoses to plastic / modern flexy tubing, however, there are plenty of people knocking about who don't do a single thing.
The one thing you will need to change is your fuel filter after 500 to 1000 miles (or when it starts to slow down!) because the chemicals in the fuel naturally clean your engine, and any crap from your fuel tank will be deposited in the filter.
Good luck!
-Pos