So what? I teach may subjects at many schools, often from different books. There is nothing in any math, history, grammar, science book that cannot be found in another book. After one book is written should we forbid anyone else from composing another on the same subject? I.don't.think.so.
Ever read any directions translated from the Chinese? I have. Both funny and confusing. The original languages of the Bible are Hebrew and Greek, primarily, translated into English. Bet something written on the same topic, today, would be much clearer to those of us whose first language is English.
However, there is value in studying translated material because of the opportunity it offers (if one takes the time) to understand other cultures, histories, and languages. I would no more recommend tossing a book because it was first written in another language than I recommend tossing all but one version of textbooks.