Simply that no one is funding it. I don't have enough spare time at the
moment to do much work on it, and no one else has stepped up. In addition,some help is needed simply for me to bounce ideas around with - it is really too big for simply one person to do it properly and viably.
I also understand that someone involved in jython has prototyped something up - unfortunately I know nothing more - I believe the jython mailing list has some details.