Open source software (OSS) is software that is developed and distributed with open access to the source code. Anyone who receives the software is free to modify it and re-distribute it.

The availability of the source code usually (but not always) results in open source software being free of charge, or having only a nominal cost if distributed by media such as CDs. 

Support for open source software can often be obtained free from the community that developed the software. Alternatively, there are many organisations who specialise in offering support on a commercial basis, especially for the most prominent OSS applications. See our open source applications page for an overview of some of the most-used applications.

One of  the most well-known examples of open source software is the Linux operating system, whose penguin logo is shown to the left.