I recently ran into an issue where our vendor wants my source code. They say they will modify and maintain the code. The only problem with this is that we are not in any partnership to develop code for each other. The extent of our business relationship with the vendor is using their product and asking them with maintenance help. The current code they want is a program outside of their product, but it performs very useful tasks. The vendor wants the source code so they can plug it into their product. What should I do?