If I release something free of restrictions to the world as a gift, that is my prerogative. And a third party’s actions don’t affect my ability to do whatever I want with the original code, nor the users of their product’s ability to do what they want with my code. And the idea of “property” here is pretty abstract. What is it you own when you purchase software? Certainly not everything. Probably not nothing. But there is a wide swath in between in which reasonable people can disagree.
If you are an intellectual property abolitionist, I doubt there is much I can say to change your mind.
Because I don’t know why it is closed source. Is it a personal project? A private project? A sensitive project? I don’t see a moral imperative for any of those to be free and open to all users.