Open Source software must follow these criteria (you can learn more at: http://www.opensource.org)

• Free redistribution
• Source code. the program must include source code and must allow distribution in source code as well as compiled form.
• derived works the license mus allow modification and derived works
• integrity of the authors source code
• No discrimination against persons or groups
• No discrimantion against fields of endevour
• distributino of lincense
• license must bot be specefic to a product
• licnese mus not contaminate other sofwares

PHP is a fine example of Open Source development and distribution. other examples include these

• apache. the web server of choice for most websites on the web
• linux. the operating system of choice for more people than microsoft woud like you to think
• bind the software providing domain name services to the internet, yes ALL the internet
• sendmail the most widely used software for transporting e-mail form sender to recipient