GPSBabel: convert, manipulate, and transfer data from GPS programs or GPS receivers. Open Source and supported on MacOS, Windows, Linux, and more. Pointy clicky GUI or a command line version...
This is the source code for GPSBabel, the free software project to manage GPS data (waypoints, tracks, routes) in your GPSes or in related programs.
We have a GPSBabel contributor guide.
Passing is good. We like passing.
The latest official release is available at http://www.gpsbabel.org/download.html.
If you aren't a programmer or a writer, we need help with gear, hosting costs, tool license prices, answering questions on the mailing lists, etc. Please support GPSBabel any way you can.
Chief Babel-Head @robertlipe