There are only six translations right now and most of them are in poor state. You can be brave hero which saves them! This time it also includes Czech translation, which I manage myself for Wammu, but I don't have time to do this also for Gammu, sorry.
If you want to add new language, just write me to email@example.com, it will be added immediately. Maybe you will also want full control over some translation, this can be also done, but for now I prefer quick translating using open (well you need to register) system.
PS: I see new testing release with improved localisation support in near future. Gettext version is working fine right now and it only needs some cleanup from unused code right now.