According to Chris Fry, StAX JSR lead from BEA, reference implementation of StAX API previewed last November will be open sourced and made available at Codehaus shortly.

Quick update, I'm in the process of moving the RI to codehaus, should take a couple weeks to get all the wrinkles ironed out, then everyone can start fixing bugs 🙂 - from stax_builders mailing list

Good.  Thanks Chris.