>Let's call it a fifty dollar program for the public to use,
>How do I protect it from most pirates?


You can protect it from all "pirates" by giving it and the source code away, and affixing a "donate" button to it somewhere.

PS - The term "pirate" does not apply to software. Pirates kill people. They steal physical things, creating real loss. But in software, if someone makes a copy of a digital work, the original work remains. The only way there could be actual "pirate" activity is if someone broke into your house or office and stole the only copy. Then you would have real loss. But apart from that, the digital world is unlike other things we've had in our lives. And it's not meant to be handled the same way as prior, physical things. Digital data can be copied unendingly with zero loss to anyone involved. It is a special gift in that regard.