There's also a practical consideration. Public versions come out every month or so anyway so the pirated version would have a short shelf life, and now that he's working on 0.8.3 new versions are coming out an average of every three days or so, every day or every other for a while. What's the point of pirating a buggy version that needs the next revision to function properly because of bugs or uncompleted new features?
Then you have to do it the next day or a couple days afterward.
Edit to Add: I just tried to count all the various revisions Grimdark produced in the month of December. I may have lost track as I ended up counting twice and getting two different numbers, but I got something like 28 revisions, at least eight of which required a new full download.
It may be that pirates just don't want to work that hard!
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