Then they probably wanted to sound hipster-wise, but nevertheless the hipster-usage of "das" rather reminds me of the following excerpt from a German comedy program: https://www.youtube.com/watch?v=l21uhFCljlU - where "das Bus" is used with a Turkish accent (the comedian Kaya Yanar was born in Turkey).
Using 'Die' for an English-speaking audience would cause more confusion, I think. Instead of thinking "The Reference", most would initially think "Who would want to kill this Referenz guy?". 'Die' in English is never pronounced the way it is in German. So while Das Referenz may be awful German, it's more evocative of German than the correct term to the English ear. Just a guess, though.
Well, they would have had alternatives. Like using a different name or just dropping the article completely and going with "Referenz". Choosing "das" seems like a very cheap attempt at copying Volkswagen style ads. Not to mention that I'm not sure there's anything connecting "encyclopedia" to "German" (as with "cars"/"engineering").
