Nifty find!
Hmm, looks like things went kinda south maybe come late 2010 with them hoping some books sold well enough to get the rest out there and keep the dev going it seems? Or perhaps the iOS version represents them taking another crack at it to get the rest going since it apparently only deals with the first 2 books?
Still, like P&P games-----more software/games need to get written for these sort of gamebooks considering they too are a treasure trove of content, rulesets, etc.