Open-source licenses facilitate free and open-source software (FOSS) development. Intellectual property (IP) laws restrict the modification and sharing of creative works. Free and open-source software licenses use these existing legal structures for the inverse purpose of granting freedoms that promote sharing and collaboration. They grant the recipient the rights to use the software, examine the source code, modify it, and distribute the modifications. These licenses target computer software where source code can be necessary to create modifications. They also cover situations where there is no difference between the source code and the executable program distributed to end users. Open-source licenses can cover hardware, infrastructure, drinks, books, and music.

There are two broad categories of open-source licenses, permissive and copyleft. Permissive licenses originate in academia. They grant the rights to modify and distribute with certain conditions. These academic licenses usually require attribution to credit the original authors and a disclaimer of warranty. Copyleft licenses have their origins in the free software movement. Copyleft also requires attribution, disclaims warranties, and grants the rights to modify and distribute. The difference is that copyleft demands reciprocity. Any derivative works must be distributed with the source code under a copyleft license.