¿Por qué no se abren los proyectos con doble click?

En la lista internacional de gvSIG, Mija ha contestado esa pregunta y ha prometido
un apaño para el hecho de que VLC Player crea que son ficheros de video.
Aquí os adjunto su respuesta:

GvSIG can't (yet) open a project by double-clicking it, in Mac OS X at 
least. So we don't reserve the .gvp extension for GvSIG in the Finder. 
The theory was that this way the icon would remain blank, so users 
would not try to open them by double clicking.

But, as you have found, someone else (VLC player) has registered .gvp 
in the system as a video format (Google Video Playlist). So that's why 
the Finder shows the VLC icon.

The double-click .gvp opening is in our to-do list, but a number of 
things must be fixed before that. Anyway, in the meantime, we will 
look for a fix for the VLC icon issue.