I was thinking - say you are put thousand of man hours and come up with a state-of-the-art CMS or something. How do you ensure that whoever get it from you does not pirate it? I could insist the buyer to give me their URL and I hash it and use it as a checksum everywhere within the software, but that sounds like a weaker form of security.
Are there any other methods? One could be to have the customer to send a POST to my server for authentication before serving any pages, but that sounds unfair.
(Of course, I could insist on hosting the software myself..)
Typically, instead of trying to find a technological solution to this problem, a legal solution is preferred. Using a legal framework of contracts and/or license agreements, make it unattractive for the customer to try to pirate or resell your software.
If your software is sufficiently desirable, people will find a way to pirate it (eg. Photoshop). If your customer is happy with their business arrangement with you, then they are unlikely to jeapordise that by pirating your software.