Use Web Service Place Finder

Hi,

I would know how activate a "appid" for use a web service of geocoding as example following :

http://where.yahooapis.com/geocode?location=701+First+Ave,+Sunnyvale,+CA&appid=yourappid

And is that I must buy a licence for use this web service in the context of an application who was developed for a entreprise ??

If yes, what are conditions to respect and of what sort is this contrat (annual subscription with token or a paiement at the consumption) ?*

Thanking you in advance.