This one's a little complex. A recent story in the 913 news magazine talked to the owners of a business called The Bar Method, where they teach fitness classes using a piece of equipment that's called a ballet barre. However, the name of the business uses "Bar."
The editor working on the story of course didn't change the business' name to the spelling "barre," which is commonly used in the ballet world. But she also used "bar" for references to the object itself throughout the story. That's something you rarely see in English writing about ballet, even though "bar" is the general translation of "barre" from French.
Would it be confusing to use both "Bar" and "barre" in the same story? I'd guess that was the editor's thinking. But I bet readers wouldn't have been confused if the usual ballet convention had been followed.