Google Translate Without API Key

Question

I am developing a mobile application that includes language translation functionality, but the Google Translation API appears to be rather expensive. If I send an HTTP request directly from the client side to Google Translate, what are the consequences? Is this approach forbidden? Additionally, what limits does Google Translate enforce—such as any IP-based rate limits? My goal is for users to have the same unrestricted access to Google Translate that they would normally have.