Add a license
Licenses describe legal rights for accessing, using and modifying code. Open licenses, which enable widespread and uninhibited use, are increasingly common, however copyleft or opinionated licenses impose restrictions that add conditions based on specific use-cases. For instance, CC-NC limits reuse to non-commercial applications, copyleft forces downstream applications to adopt an equally permissive license for any derivative works, and numerous other licenses are aligned with specific social causes. The Hippocratic License hosts a tool for creating a custom license, including explicit allowances and restrictions for various potential use-cases, such as a Fossil Fuel Divestment module, a Law Enforcement module, and a Supply Chain Transparency module.
Visit choosealicense.com for an extremely detailed survey and comparison of various software and non-software licenses. There is also a page describing what happens if you don’t choose a license.
Note that software licenses are often distinct from licenses intended for non-software materials, such as data, media, documentation and fonts.