shareware enforcement vs time machine

Question

Problem: Customer X is (considering) porting one of his formerly "Windows only" shareware applications to Mac OS X. One of his concerns is how to enforce the 30-day trial period and make it immune to "system rollback" software like Time Machine.

Question: What is the industry best practice for preventing the use of "system rollback" software to lengthen or otherwise modify a 30-day trial period on shareware?

DISCLAIMER: I do not consider the strategy of Customer X to be a viable one, and I don't see how people will have the incentive to rollback their whole system just to use his software for a few more days. Nevertheless, for the sake of due diligence I ask here just so I can research his question. Please consider this if you wish to down-vote merely because you (and I) may disagree or find this impractical.

Answer 1

Usually OS X developers use a hidden file in one of the support folders somewhere with the trial date in it. For the most part this is a good enough strategy for what he wants, I doubt anyone will do a full system restore just to pirate his application, and if they use Time Machine to restore the application bundle itself from an earlier date, it won't make any difference at all to the trial date.

Now, if he is worried about users doing a full restore or tracking down the hidden file, he could try some sort of online validation service for his trial software. Really though, those people are just going to find a cracked copy anyway, which you can't really fight even if you wanted to put the time into it.