Hopefully you caught Alex's Understanding the Second Generation of Behavior Trees, simulcast live as an AiGameDev.com broadcast and an AltDevConf presentation. During the broadcast Alex announced that the Behavior Tree Starter Kit would be free to AiGameDev.com ULTIMATE members. Here is that release.
Behavior Tree Starter Kit Source Release
Alex J. Champandard on February 12, 2012
Access the rest of this feature by joining industry experts and other professionals as an ULTIMATE member in the leading Game AI training program.