Morally, however, I find the GPL repugnant. Its fight-fire-with-fire principle of forcing anyone who uses a piece of software to disclose all their source code in turn betrays its purported ideals of freedom in a disgusting way.
The GPL does not force users to disclose source code. Source code is only required when distributing GPL software to others. In fact, if you’re only using GPL code you don’t even have to agree to the license (sometimes that’s misunderstood too). That is, you’re free to disagree with the license yet install and use the software. Therefore, the GPL respects your privacy and asks only that when affecting others with copies of your software, you give them the same freedom you have. There’s nothing morally repugnant or disgusting about that.
Via J.B. Nicholson-Owens.