need some info/help on licensing

[apm]

Hi,

I have created a program in php3 which will be used by other compaies to provide certain services.

The problem here is is i am  not intetrested in a GNU/GPL license as it will not be free. What sort of a license would i require if the company buying the program needs to run it from their server , since i will be distributing the code... i  want  to make sure they cannot make any changes in the code without telling me first. These are big companies so i guess a bit of trust and integrity are there(although i doubt it. SO the license woulkd givem them the right to run it from their server but they cannot use the edit or change the ocde.

DOEs any  know of this sort of a license or can point me in the right direction or suggest some links. I would very much be greatful.

Thank you.
Apoorva