AFAIK Ben was a survivor and has been with Mackie since Greg's time around 2002 Greg left in 2003. It must have been pretty frustrating to work under a bunch of bean-counters and probably had enough or the offer from Amazon was that good. I don't know if he had any hand in some of the code, he had his masters in the UK in DSP technology. He may also have enticed some of his fellow Mackie friends to go with him.
P.S. You can also look at it another way and say that he didn't finish his pet project and instead killed it. Traditionally Mackie's software department has been a revolving door.