According to the St. Petersburg Times ...
<< When Doug Waechter was warming up to pitch in Boston on Thursday, he didn’t have a good feel for the split-finger fastball he had debuted in his previous start.
He fidgeted with his grip until it felt comfortable and ended up somewhere between how he holds the ball for a splitter and how he holds it for a changeup, with his index finger on the side of the ball and his middle finger on a seam.
From that, the “splange” was born. >>
It sounds to me like a forkball / splitfinger fastball with a slightly altered grip.