Share and Share Alike: Understanding and Enforcing Open Source and Free Software Licenses

Abstract

This paper describes the history and the commonly used software licensing terms of the free software and open source movements. It explains the GPL and discusses attempts to enforce the GPL. The GPL is a revolutionary copyright license that has allowed software developers to use existing law to copyright their work, while allowing licensees the freedoms to use, copy, modify, and distribute their work, but not to turn the work into a proprietary derivative. 2005 brought two notable efforts to enforce the license in court. A district court in Munich, Germany declared the GPL valid and enforceable. Meanwhile, litigation between The SCO Group (SCO) and International Business Machines (IBM) may clarify how U.S. courts will interpret the GPL.

Keywords: software licensing, free software, open source, copyleft, GPL, GNU GPL, copyright, software, copyright enforcement, OSI, FSF