How does copyleft work?
To understand how Free Software works, it is necessary to see how copyright can be used for creative works we write, including software. All of us are aware of the copyright law, and how most people use it. For example, a book published by MIT press, titled Philosophy of Computing Information has this on the copyright page: © 2004 by Blackwell Publishing Ltd All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs, and Patents Act 1988, without prior permission of the publisher. Many of us have seen such statements in most books. The copyright law says, the author or the copyright holder can specify the conditions of using the resource. But, as the history of its usage suggests, almost everyone in the world used it to restrict the way the resource can be or cannot be used by others. Only one
