This assumes that writing and selling proprietary software is 'the ability to control other people'. Making a program proprietary is controlling people, pure and simple. It is a matter of restricting users from sharing, studying and/or changing the program--restricting users from cooperating. but people *choose* to accept the restrictions of non-free software for any number of reasons. People often choose to give up important freedoms--usually because they are offered a limited choice, and the other alternatives seem to involve short-term pain. One can understand why people do this, but the effects are still dangerous. When almost everyone gives up certain freedoms, those few who keep them may be subject to various sorts of pressure that only a few determined people would resist. The crucial question is not whether people had some limited range of choice available. It is, what limited the choice? Was it limited by nature, or did someone deliberately deny people the other better choices? And if so, was that wrong? I do not see anyone being coerced into using it by threat of physical force. Physical force is not the only thing that can hurt people or systematically degrade society, so whether it is employed not a crucial issue. But, as it happens, physical force generally does play a role in proprietary software. Most proprietary software developers make use of laws that place the power of the state at their service in stopping users from sharing. Using physical force is sometimes justified--for example, to prevent a wrong. In this spirit, copyleft uses laws and state power to prevent others from using the very same laws and power to restrict users.