Google Maps and the services related to them that enabled the embedding of a map on websites are now monetised. The monetisation is directly related to the traffic your website receives, so please check Googles pricing page for more details on this.
Whether you pass this traffic threshold or not, in order to get your maps working on your site you will need an account complete with billing details in order to obtain the API key your developer will request. Please see below for a great third party tutorial that will take you from start to finish for succinct setup:

Jason Danes
Support Team