[Tdol]

There's nothing really dodgy- if it's copied, it's an infringement. Many definitions will naturally be almost identical, but it is a matter of trying to weed out those that are copied from original wordings. If enough words were changed that it did not resemble a straight copy, it would be acceptable. If hundreds of idioms were identical or differed by one word, then that would constitute an infringement. If a few get past the filter, then I doubt that much would happen. They don't appear on the site immediately, so there are opportunities to deal with this.