Thanks for the reply. Got a little further. And "Yes", I read the manpage, a good deal of the site. grabbed the sources, and scanned the mailing list - before posting here. (Also got a reply from the maker's "support" email - which was not helpful.)
In the first pass, only saw NMEA output on the serial port (not USB or UDP). Was using a USB-to-serial (DB9) cable with the wrong gender on the DB9 end - so rigged in a female-female coupler. Was good enough to get NMEA output, before it fell apart. USB-to-serial cable of the proper gender arrived tonight - so will try again on Tuesday.
This device is old and quirky, takes a bit to figure out what works. :/
Seems the device also responds to SNMP ... kinda. (Serial looks like the best bet.)
Again, not expecting an easy answer, but have to ask. :)