Shafid,

Ask them their purpose. If they intend to resell, you can reasonably expect a cut. If they want to control it themselves, it depends how easy it is for the customer to rewrite it themselves and cut you out that way. If you want definitive advice, try "IT Law" in Auckland- they're a boutique firm that specializes in IP issues like this. Might be worth spending a few hundred $ to extract a decent fee from the customer. Also be aware that there are law firms (including in NZ) that encourage theft of intellectual property from people like you, confident that it's simply not worth the $thousands and $thousands of costs for you to take the matter to court. If it reaches that point, you'll get nothing. How well do you know your customer? ;-)