Viking is a free/open source program to manage GPS data. You can
import, plot and create tracks, routes and waypoints, show OSM
and other maps, generate maps (using Mapnik),
see real-time GPS position, Geotag Images,
control items, upload/download OSM Traces and more.
It is written mainly in C with some C++ and uses the GTK+3 toolkit.

The following options can be enabled (by default, they are disabled):

MAPNIK=yes     for rendering with Mapnik (requires mapnik)
GEOCACHES=yes  for geocaches acquire