We are Romanians. My DD is learning English. He sings and speaks the solfeggio in Romanian (Do, Re, Mi, Fa, Sol, La, Si, Do - so we have Si instead of Ti) although he hears clearly the Ti in Hellen's music chant and when I sing or speak out loud the 6th note.
SM is using images easy to recognize in our language: door, rain etc. And sometimes is easier to ask him in the native language where the door is or the rain instead of asking about the note, though he understands the English words.
There are just few notes so very few words for a child to understand and for a parent to translate from to make it easier when using SM in English.
As for the rest of the materials, for instance for the flash cards you don't need to know English. As for "Kingdom of Tune" book - and here
NadiaD can confirm or not - just like any other story, you can create your own materials in your language to be used with your child, according to what is most suitable or what you know she enjoys best. You can be very creative. NadiaD showed us while using the coloring page to talk about what's in the drawing. In
her video
she's speaking in English, but anyone can do it in his native language, right?
The more important thing is for the parent to understand what and how to use the SM software / games. As a parent, you're the one guiding the child and for that child practicing is the most important for learning, not the language of SM.
Andrea