Please could someone give me some good advice.

We have a business system that we "license" to operators for the use of our system. We dont want to go down the road we have of recent, so we would like to request an amount of the fee upfront as a part payment of the total fee, merely to dissuade people that are not seriously interested and other who wish to replicate our concept for free.

The "deposit" will be set off against the total price if the deal goes through and refunable if it does not.

My question is can we call it a deposit, if not what do we call it, and can we safely do it?