A friend today asked me whether I thought that the license for his software project (GPLv3) was potentially keeping people from adopting it. The short answer is is yes, but I figured I could expand on that a bit. And before I get too far: I am not a lawyer, I am not your lawyer, this is not legal advice, please seek competent counsel in your jurisdiction for advice. Instead, I want to talk a bit about why different licenses exist and what they mean.