Hello, for now you can get an api key thought the RapidApi page (you can retrieve the url here https://gas-api.ovh/).
I plan to open the access to the direct api key in a few weeks.
Yes, for now you can use it through the RapidApi proxy : https://rapidapi.com/EdouardQ/api/gas-api3
Later I will open the account creation for direct access to the api.