welcome to the MH forum and sorry for answering late, I wasn't around for quite a while
As one of the creators of the German language file, I know that the translations for undo and redo are too long but at the time I created the file I had no better idea how to translate it instead. At least the meaning is correct and that was the most important thing for me.
Also, the makehuman GUI is not finished yet as Makehuman still being in alpha stage.
All the makehuman language files are to be found in ...\makehuman\data\languages and can be modified from here.
I cannot speak for the makehuman team officially, but they always need help and if you think you can participate with anything I think it is best to just shortly contact the project owner, Manuel, and discuss things with him.