The SOAP interface allows you to integrate the Musipedia search engine into your own application.

You can find the interface, as well as its documentation, under this URL: 

http://www.musipedia.org/soap/

The WSDL document is here:

http://www.musipedia.org/soap/?wsdl

Yes, until further notice and as long as nobody increases the load so much that further investments in server capacity become necessary. But please let me know what you are building using the SOAP interface, and how many queries per day you anticipate.