Z:gnu-www-ja-quick-guide-gplv3--61d269-You're probably familiar with/en

You're probably familiar with the Digital Restrictions Management (DRM) on DVDs and other media. You're probably also familiar with the laws that make it illegal to write your own tools to bypass those restrictions, like the Digital Millennium Copyright Act and the European Union Copyright Directive. Nobody should be able to stop you from writing any code that you want, and GPLv3 protects this right for you.