Using the API is FREE...
Commercial projects should consider a yearly donation to keep the site running and pay for our servers and bandwidth but this is not essential.
Testing/Private project API Key
NOTE TO Developers: If you want to test the API or are only using it for a personal project you can use the Test API key "1". Please don't use this in a production environment with multiple users though. It may be rescinded at any time.
Production API Key
To apply for a production app API key follow this link:
http://www.theaudiodb.com/api_apply.php