Title: OpenCPN chartplotter navigation
Homepage https://opencpn.org
There are few, if no alternatives. This is a popular chartplotting program for yachts. There are versions for OpenSUSE, Ubuntu, Fedora, etc.
It is open source link is https://github.com/OpenCPN/OpenCPN/tree/v4.8.0
Latest version (master) is 4.8.2 dated 2/28/2018
Thank you