The premise of copyleft licenses is attractive: Create more open source! With permissive licenses, someone can take the code and make proprietary modifications to it and sell it to other people without releasing the modifications. We want people to publish their improvements, right? With copyleft, we can force people to publish their improvements to copyleft code. Businesses will want to use our code because creating it was so much work in the first place. We need copyleft if we want more contributors, more open source, more code re-use, more freedom.
Free Software is an abject failure. It may sound like a good concept on its face—especially with the kind of language often used to describe the movement and its opponents—but, when put under scrutiny, the institutions and practices that make up the Free Software movement fundamentally fail at their stated goals and harm the software ecosystem as a result.