ShareAlike

ShareAlike is a licensing term used in several open licenses, most prominently in Creative Commons licenses. It requires that derivative works based on a licensed performance, artwork, text, or other content be distributed under the same license terms as the original or under a license that the rights holder has deemed compatible. The goal is to preserve the freedom to reuse and adapt works while ensuring that downstream derivatives remain open.

In practice, a work released under a ShareAlike license, such as CC BY-SA, allows others to remix or adapt it as long as attribution is provided and the new work is licensed under the same or a compatible ShareAlike license. Attribution is a separate requirement (for example, the “BY” component), while the ShareAlike condition governs the licensing terms of the derivative.

Benefits and limitations: ShareAlike helps keep derivatives open and shareable, promoting collaboration and ongoing redistribution. However, it can create licensing incompatibilities with works that use licenses without share-alike terms or with distribution models requiring different licensing. Some researchers and developers view it as restrictive for commercial use or for combining with proprietary content.

Examples and usage: The CC BY-SA and CC BY-NC-SA licenses employ the ShareAlike condition. It is also associated with the broader copyleft philosophy, wherein freedoms to use, modify, and share are preserved across adaptations. The approach is widely used by open-content projects, including many encyclopedic and educational resources, to ensure ongoing openness of contributions.