I don't think it's possible at that time to change Natron language ( I may be wrong but I think everything is written directly in the code in english, so it's hard to make a translation system from now) .
Being non-English native, I found a bit hard at first to understand software that was not written in my language. I started to get into computer when I was 12 and with no english knowledge beside yes , no , ok or cancel ...
That doesn't stop me from learning all that stuff even if I used word that I didn't understand at that time. Words like roughness was something a bit abstract to me but I know what it means in the 3D software that I used.
Even now I strongly recommend people to stay with the english version of the software, even if they are not fluent in english, because translation are not very well made.
Even in english you can find various word for the same thing from software to software, when it's translated to another language it get worst to say the least.
I'm french and in french language we haven't word to describe things like glow , glare or glint, so translators found words very abstract for it, and sometime it's impossible to make the link between the translated word and the original english version, it just add some confusion and you end up loosing time.
In the other hand , even if you don't understand the world glow at first, if you understand what it do , in every software you'll get a chance to find the same name. In translated software it goes by many names and you finally get lost.
As not beeing english native speaker I found a bit sad that it becomes the international language , that if you don't speak english and want to do CG or programming you'll have and hard time... but at least all words are nearly the same from software to software and from programming language to programming language. In translated version it's clearly not the case.
Natron was written by french people, but the software isn't in french, that could have been the case if we were in a fair world... (but I'm trolling a bit now) ...
I think this guy had to learn a bit of english if he want to get into the CG world...