This document discusses the history and evolution of open source software. It begins by defining open source software as software with source code available under an open source license allowing anyone to use, modify, and distribute the software. It then summarizes the key events in open source software's history, including the development of the open source model in response to the free software movement and Netscape's 1998 release of source code for their Netscape Communicator browser. Finally, it discusses the founding of the Open Source Initiative in 1998 to promote open source principles and clarify the benefits of open development models over closed, proprietary software systems.