Open-source license

Open-source licenses are software licenses that allow content to be used, modified, and shared. They facilitate free and open-source software (FOSS) development. Intellectual property (IP) laws restrict the modification and sharing of creative works. Free and open-source licenses use these existing legal structures for an inverse purpose. They grant the recipient the rights to use the software, examine the source code, modify it, and distribute the modifications. These criteria are outlined in the Open Source Definition.

After 1980, the United States began to treat software as a literary work covered by copyright law. Richard Stallman founded the free software movement in response to the rise of proprietary software. The term "open source" was used by the Open Source Initiative (OSI), founded by free software developers Bruce Perens and Eric S. Raymond. "Open source" emphasizes the strengths of the open development model rather than software freedoms. While the goals behind the terms are different, open-source licenses and free software licenses describe the same thing.

The two main categories of open-source licenses are permissive and copyleft. Permissive licenses come from academia. They grant permission to modify and distribute software. They usually require attribution, and they disclaim warranties. Copyleft licenses come from the free software movement. They require derivative works to be distributed with the source code and under a similar license. Since the mid-2000s, courts in multiple countries have upheld the terms of both types of license. Software developers have filed cases both as copyright infringement and as breaches of contract.