Open-source software (OSS) is computer software that permits users to study, change, improve and at times also to distribute the software.
 Spreading of Open-source software
Free and open-source software has become a mainstream phenomenon in the twenty-first century and is pervasive today. (From the software used by organizations, open-source is expected to rise to thirty percent by mid-2012. In 2011, about thirty percent of the total software expenditures in the United States were for the development of prepackaged software; thirty-five percent were for custom-developed software; and thirty-five percent for the development of software for internal uses.)
The Linux operating system is one of the most widely known examples of collaboratively developed open-source software. However, it is only one of many thousands of such projects. Many mainstream companies, such as IBM, are contributing substantial resources in support of Linux and other open-source projects.
Software companies that provide open-source software to their customers generally recoup their investments through the sale of services (e.g., to install, maintain, or customize the software) or complementary assets (e.g., proprietary add-on programs that perform specialized functions).
- Alison Diana. "Open Source Approaching 30% Of Enterprise Software", InformationWeek, February 09, 2011. Referenced 2011-10-10.
- U.S. Bureau of Economic Analysis. "Data Tables: Software Investment and Prices by Type" (xls), U.S. Department of Commerce, (last updated Aug. 3, 2012). Referenced 2012-08-12.
- Pamela Samuelson. "The Uneasy Case for Software Copyrights Revisited" (pdf), The George Washington Law Review, September 2011. Referenced 2011-10-10.