Customization on a PHP script

Hello, I have a php script which is related to Real Estate. Need to have it customized to my needs. Need adjustments done,. Basically the application has everything that I want. I had got it developed quite sometime back. Now I look at getting it enhanced and make it better. Whoever wishes to bid, need to understand that, they would have to give in writing that they cannot use the same code for any personal or commercial purpose. Also they would not be able to showcase the work to anyone. However this application would be required to be enhanced on a regular basis and the winner of the job would be getting it regularly and no one else would be given access to the same. Serious freelancers may only bid. Regards