Copyright has one of the most fashionable legal tool of recent time. Every author tries to create a monopoly over his/her work. Copyright law has gone through a series of changes to become author friendly and granting sufficient rights to authors over their work. While the copyright law was gaining confidence, there were a group of people who were not very excited about these rights. They believed in distribution of work and collaboration between authors for better community. They revolted against the copyright law by creating something called copyleft. Copyleft is a philosophy where the authors believe that their work should remain free and everyone should be able to gain access to their work, use it, modify it and redistribute it. They used the existing copyright regime to convert it into a dispense rights rather than curtail them. In this paper, I have tried to present an overall understanding on what is copyleft and then compare it with the existing copyright laws. At first instance it seems that copyleft is opposite to copyright but I have tried to present how copyleft works within the copyright regime and not against it. The copyleft has not been legally recognised through a legislation, thus creating a doubt a on its enforceability and validity. I have tried to present a compilation of different laws and cases which would elaborate how copyleft agreements are valid contracts and can be enforced under copyright law sand contract laws. Establishing copyleft agreement as a valid contract would provide the licensor and licensee more trust and belief in the philosophy and help them gain certainty for the protection of their rights. Copyleft is a Marxist approach to combat the proprietary software models to break the girdle of monopoly and provide and spread knowledge to the masses.