Im really impressed by pam_abl. It covers every pam enabled service so smart password guessers which may traverse between protocols will be covered as well. It's configurable as to how to handle guesses from hosts as well as users.

Systems and methods are provided for auditing and selectively restricting software usage based on, for example, software copy counts or execution counts. In one embodiment, the method comprises verifying whether the serial number for a software installed on a computing device corresponds to one of recognized serial numbers, and calculating a copy count (or software execution count) for the serial number. In response to the copy count exceeding a defined upper limit, a limited unlock key may be sent to the device. The limited unlock key may allow the software to be executed on the device for a defined time period, a defined number of executions, and/or with at least one feature of the software disabled.

This sounds to me like a really general way of copy protection, yep another rotten software patent in my books.