Every legitimately-operating company will have such terms and conditions - without them company would not be able to operate legally. No legitimate company will ever say you that you can submit the paper, full stop.

When you look for the company to give your dissertation ensure it is legitimate UK or US Company, speak to them, ask questions. Check the company (in UK via companies house, I am not sure about US). Maybe give them a small task to complete and see the quality. And only then decide which one you would go for.