From the GIMP-gui mailing list:

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Dear developers

I started using gimp 2.10 about a 2 - 3 days ago. I would like to point out some incorrect translation term  in greek about a menu item, and this is the brush tool "brushes mypaint". 
The current translation of this brush tool in greek is "πινέλα η βαφήμου"  but because mypaint is a program, I believe the term "mypaint" must be  untranslated in greek.  
This brush tool translation in greek version of gimp 2.10, should be: from "brushes mypaint" to "πινέλα mypaint"  a fact that indicates the use of brushes (πινέλα) from this particular program. 
I hope I pointed out correctly this enhancement bug and that you will soon take care of it. 

Sincerely yours
Vasilis Stasinopoulos
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I'd say that depends if MyPaint itself (i.e. the program name) is translated in their official Greek translation (if they have one), but it's better to let the translator decide. So here it is.