>>>Yes, I agree that "subscription" is correct term. I am just not sure if it can apply to my application since it is not web-based. If it were web-based it would be easier. I am still thinking if this is correct and legal approach.
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>>I don't see how web-based has anything to do with this term.
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>>Doug
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>I meant that if the app was web-based on my server turning the subscription on or off would be easier. And I think it is more common to do it that way. For example, www.ariba.com do it that way with their application. They sell license and then charge for subscription. If a customer does not pay, the application cannot be used.

There are two ways to enforce this. One is to let the application do a subscription check online, you have a webservice where you can control the subscriptions based on the licenses or IP address of the clients. If the client must be able to work without an internet connection you can provide a certain time range that the program does not need to check before locking up.

Second option is what we use frequently in accounting packages, since they must have a periodic closing function, to let the user type in a closing code. The closing code is only provided when the client has an active subscription. This model requires more maintenance, but it depends how many clients you have or if you have distributors that take care of the subscriptions.

From a legal aspect you need to be careful, because the locking of the entire application could be doubtful. I have seen cases where the judge decided for the client, even though he is not paying, the existing "Data" is the property of the client. So if you lock the application in such a way that the client cannot get to his existing data, that could be a problem.