Could you try to change the font in /opt/cloudgps/cloudgps.ini to something else that supports Greek letters and report back if it renders correctly? Would you care sharing your Greek keyboard layout so it could be included in next version?
sudo sed 's/^ttfFont=.*$/ttfFont=\/opt\/usr\/share\/fonts\/nokia\/Nokia_Sans_Maps.ttf/' /opt/cloudgps/cloudgps.ini -i