All I know about boysenberry is that it is in ice cream. I believe I had it first at Braums (not having had it in Australia) and I got it because of the novelty factor of the name. Pretty good stuff (but why no girlsenberry?). I also have had some boysenberry jam from my sister-in-law that she bought for Kate. Also pretty good.
The only boysenberry reference I know of is in the song Punky’s Dilemma by Simon and his not-as-talented co-musician. Kate remarked - when we were dating and at Best Buy getting a cordless phone for my mom - that she liked it. So I searched the CDs and found it only in a 3-disc ‘best-of’ collection which we still have. It was one of those do-it-to-get-the-girl-to-like-you kind of things.