What you need to do is one of a few things.. Look into the various forms of licensing, What kind of app is this? Could you, would you want to, devote an entire computer to it- Could you have a unix box to serve the running software to the LAN? We do something like this also. Make software for offices. I am not worried at all about protecting the code. I want people to use it, steal it. The more free I am with it, the more chances that:

• others will keep my name, company references, in the code- Since they don't have to do anything secretive about using it.
• More people will use the code, which spreads the word.

Think of something like apache. Or CGI.pm. It is widely used, free- Think of Linus Torvalds, Linux is free- and I don't think Torvalds is going hungry. Linux is widely used, and it has dude's name on it. If you need help with linux, if you could choose, you might choose Torvalds to help you out. So.. There is much more power in letting people have it, and use you as a reference.

You mentioned this is for a client. I imagine what you are doing for them, could be done for other clients, right? Well.. How many clients can you possibly get with some obscure software only crazy computer geeks understand, and only you really know of? If your software was freely available, I may use it for one of *my* clients. And guess what.. If I run into any problems, I could probably ask you for help. If I really really needed some help, I might even hire your company to do it for/with me. .. None of this will happen with your hidden proprietary code.

I suggest it's just not bad,.. but.. sketchy- karma. Since p3R1 is.. sort of.. inherently open source.. right? The whole thing got so good out of being vulnerable. Think.. think love. Love is open source. Unless you let it be seen by your partner.. it won't fly. So.. Don't be scared.. show your love.