The idea was proposed to Stern in 2006, long before the recent local interest. In more recent times, A Metallica, Led Zeppelin, another KISS and the AC/DC pin were proposed to Gary Stern, but the license was not approved. I know for a fact the KISS license fee was "through the roof". I think Stern's lack of interest, or the prohibitive fees prior to 2006 would have been the catalyst in the home brew AC / DC pinball;
I'm very pleased it is happening, and this might be the pinball that reignites the industry !