GpsPrune is a map-based application for viewing, editing and converting coordinate data from GPS systems.
It's a cross-platform java application, and its home page is at https://gpsprune.activityworkshop.net .
Here on github you'll find all the sources from version 1 to the current version 27.1, and bug reports and suggestions in the form of "Issues".
In the wiki at https://github.com/activityworkshop/GpsPrune/wiki there's the beginning of a translation effort for anyone to contribute. Currently just a few of the missing texts are online, to see whether it's a workable idea or not. Please help with these if you can. Or if you prefer, contributions to the translations can be made using the Translatinator at the GpsPrune home page.