If you are asking "do I need to have separate accounts on Google for separate API usage?" then the answer is no, you don't need to. You can if you wish, but the APIs are part of a project associated with an account, and an account can have multiple projects.
If this is in relation to your purchase of "(NE) Translate" than the above is the limit of my support for you on the Google API side of things - the instructions in the application are clear and precise. If you have issues getting the API configured, or questions on costs etc., then you should contact Google for assistance.