What is Open Source?

Open Source is both a philosophy and a development process. The philosophy centers around the idea that the development of the source code (computer code) of an application should be open for all to see, to use and to contribute to the growth  of that resource. Also, that development can be used to expand the initial intended use of that application and that for source code is not sold but is free of cost.

The development process is shared by those that use the application and in most cases there are a group of persons who oversee the development of the core code of the product. Deliberately obfuscated source code is not allowed.

"The license may restrict source-code from being distributed in modified form only if the license allows the distribution of "patch files" with the source code for the purpose of modifying the program at build time. The license must explicitly permit distribution of software built from modified source code. The license may require derived works to carry a different name or version number from the original software."  _{Open Source Initiative Website}

You can read more about Open Source at The Open Source Matters Website.