I'm looking for a list of SAX based XPath Implementations that are
implemented in, and callable by, java programs.  Preferably, it would
have an open source license or a redistribution fee of less than
$1000.  I saw a few research projects out there, but none of them
seemed to be ready for prime time (i.e. commerical grade).

Hi, ehuddleston-ga:

XPath, although crucial to several XML "technologies" like XSLT and
XPointer, is not itself syntactically XML based.  This has led several
to suggest that an XPath API might be standardized apart from XML, by
analogy with the SAX API development/standardization (and possibly by
leveraging or otherwise relating to that offshoot).

I found the discussion here to be useful:

http://www.xml.com/pub/a/2001/03/07/xpathapi.html

In "Internet time" of course this is a pretty old treatment.  I could
try to provide a state-of-the-art treatment as an Answer for the list
price offered, but I don't have any assurance that what you are
looking for exists.

regards, mathtalk-ga