...You can import, plot and create tracks, routes and waypoints, show OSM, Bing Aerial and other maps, geotag images, create routes using OSRM, see real-time GPS position (not in Windows), make maps using Mapnik (not in Windows), control items, etc.
It is written in mostly in C (with some C++) & the GTK+3 toolkit.
Viking is currently dual managed - with a corresponding Github presence at:
https://github.com/viking-gps/viking
Where you may find it easier to view the code and raise issues there too.