BEA's reference implementation of StAX (Streaming API for XML, aka JSR 173) was open sourced at Codehaus back on May 12 but the announcement apparently didn't reach me so I just found out about it by loitering at the StAX Yahoo Group.
StAX website at Codehaus is lacking essential information for the moment but you can get the source from the CVS:
cvs -d:pserver:firstname.lastname@example.org:/scm/stax login
cvs -d:pserver:email@example.com:/scm/stax checkout stax
FYI, stax/dev/src and stax/dev/src100 were identical last time I checked. Don't forget to join the StAX Yahoo Group to communicate with rest of the StAX fan club.