The hardcoded menu entries in the first application menu are localized by :NSLocalizedString(@"string", nil), e.g.
[NSString stringWithFormat:NSLocalizedString(@"About %@", nil), aboutName]
so that the file Localizable.strings in the language folder /Resources/<lang>.lproj can substitute the menu entries
In the attachment there is a numbered extract with the changed lines in tkMacOSXMenus.c
I will look into other files, too, but what is done is done ...
Great project!
Zbigniew
changed lines for localization