I have a NMEA USB GPS Puck and I want to use Google Earth for GPS on my Mac Mini; OS X 1.4.3

I downloaded GPSBabel 1.2.5 for OS X, but discovered that it only does live Garmin and Magellan conversion.

Is this a feature that was simply not included with the build, or does GPSBabel not do NMEA live conversion at all?
Is there a build of 1.2.7?

I am cutting things close, leaving on a long road trip next week.