Software license

A software license is a legal instrument governing the use or redistribution of software. Under copyright law, software is protected as a literary work, and a license grants the user rights that would otherwise be reserved to the copyright holder. Licenses may impose conditions such as payment of fees, restrictions on modification, or requirements to distribute source code. The choice of license affects how software can be shared, sold, or incorporated into other projects.

Types of software licenses

0 license: grants limited rights, often restricts copying, modification, and redistribution. Examples include Microsoft Windows and Adobe Photoshop.
0 (FOSS) license: grants rights to use, study, modify, and redistribute. They are further divided into:

** Permissive licenses (e.g., MIT License, Apache License): allow use in proprietary software with few restrictions.

** Copyleft licenses (e.g., GNU General Public License): require derivative works to be distributed under the same license terms.

0: software with no copyright restrictions, such as CC0 or Unlicense.

History

Early software was often distributed without explicit licenses, but the rise of proprietary software in the 1970s led to shrink-wrap licenses. The Free Software Foundation and GNU Project in the 1980s pioneered copyleft licenses. The 1990s saw the Open Source Initiative define the Open Source Definition. The 2000s introduced new licenses for web services and cloud computing, such as the Affero General Public License. Today, hundreds of licenses exist, and tools like SPDX help standardize identification.

Features of software licenses

Grant of rights: what the user may do with the software.
Restrictions: what is prohibited (e.g., reverse engineering, sublicensing).
Warranty disclaimer: most licenses disclaim liability for damages.
Termination: conditions under which the license ends.
Governing law: which jurisdiction applies.

Software license