Hello, I usually do not answer questions on forums. I am not a coder just an retired investigator and the frustration I get when people think that the law works in the normal scope of your daily lives. When, in fact the law is in its own world. What you think is not debatable in the laws eye's its debatable. I understand your frustration as "its mine and it all mine". However, the law is all about the shades of grey. A letter stating Cease and Desist is just words if you do not provide any foundation for that issue. There are a couple of questions you need to ask yourself, so you do not have bad days. 1. Who has most to lose? 2. Who has the most to gain? 3. Who can sustain legal conflict? 4. Who is within the law. You made a few comments that in my world I would address if I was interviewing you, if you can answer them honestly then it may help you in your quest. 1. If not work for hire, was work done on a volunteer assignment. 2. Do you work and get paid for your services as a employee or a independent contractor? 3. Did you use or copy code from others sources or app services to combine code for the app? 4. What is your legal basis for claiming rights to your code? 5. Does your coding violate any other patient rights or trademarks? 6. Have you filed any Copyright claims to your code? You get the idea and the reason I am stating this, if they decide in a legal battle you will have a deposition and many more questions will be asked. Like I said I understand your frustration but, you also have to understand that unless your willing to loose allot of hair at night rethink your goal. If, not I would recommend an Attorney to write a letter and here is the reason. They will pass your letter on to there legal department if they have one. They will notice that a novice wrote it without any legal foundation you will be round filed. They also know you have no funds to fight in legal environment and guess what they may file against you. Highly recommend take the few hundred bucks and spend it on a attorney to write the letter, they will include any legal foundation for you. So, good luck and I hope this at least allows some clarity for you to think about.