I'm no lawyer, so take my interpretation with a huge grain of salt here, but I believe that the TOS allows you to charge for services that are supported by the API, but you cannot charge specifically for access to charts built on the API. Also, the TOS strictly forbids downloading or otherwise obtaining the source code for the API, which would probably prevent you from putting the code in escrow.
In all likelihood, the generic license agreement does not meet your specific requirements, so you would have to have a special one drawn up (assuming Google is willing to do so).