Here's a somewhat contrarian view - if what you are making is so good (or unique/special/non-trivial) that it is valuable to more than just one huge customer, t

Here's a somewhat contrarian view - if what you are making is so good (or unique/special/non-trivial) that it is valuable to more than just one huge customer, then just because they are huge and you are seeing dollar signs, doesn't mean you should agree to their request without due consideration. They may attempt to compete with you or re-implement what you do, but again - if what you did is so good and perhaps non-trivial to re-implement (an assumption), then you should consider the value of what you have above their immediate demands. They might not have to be your "only" customer. If you are trying to build a business to last on your own, you must ask yourself, is this the kind of customer I want? Of course, you should consider who the customer is and their mission/vision/values/actions, what your and their goals might be in this instance, how to accommodate their request (like the suggestions for code escrow, etc.) while protecting yourself (surely there are ways through a competent IP lawyer). Sometimes the big customer can break (or make) your company. I think your course of action depends a lot on what you have and what you want. That they are interested in you so seriously is probably a good sign, as much as it is something to be concerned about. Consider the value of your use case and what it might be to others as well. This might be me being naive, but, if they will be good to work with, and a good customer to have, they will be willing to work with you fairly. Otherwise, be cautious and consider the calls for legal advice.