Making Money off of Yahoo maps API

Hello,

I am in the early stages of developing a website which will incorporate Yahoo Maps API. In a nutshell, I plan my website to allow a user the ability to map a location, grab the map image of a location, insert directions and other relevant information in a Paint-Like imaging platform. Check out www.productionmaps.com I want them to be able to create a map like this. I do plan on making money from this, If legal, I'd like to charge the user a small fee for creating a map, but if this breaks the terms of service I can make money just on site advertising if I have to.

I'm wondering if I'd be breaking Yahoo maps terms of service if I use their free API in this way.

thanks.