A software licence is a legal permission or set of permissions governing how software may be used, copied, modified, distributed, accessed or otherwise handled. Copyright law generally gives the copyright holder exclusive rights over activities such as reproduction and distribution, while a licence grants specified rights to other parties subject to stated conditions. The term licence therefore does not necessarily mean that the user owns the copyright in the software.
A person may have a licence to use software without acquiring ownership of the underlying intellectual property. Software licences can be proprietary, open source, free software, permissive, copyleft, subscription-based or otherwise structured. The exact rights and restrictions depend on the licence text and, where relevant, applicable law and contractual terms.
Proprietary software licences commonly grant users a limited right to use software while restricting copying, modification, redistribution, reverse engineering or other activities, subject to applicable legal exceptions. A licence may define how many devices or users may use the software, whether commercial use is permitted, how long access lasts and whether transfers are allowed. Software can also be provided under subscription terms in which continued use depends on maintaining a subscription or account. These arrangements can coexist with ownership of a physical copy or access to downloaded software. The legal relationship can be complex because copyright, contract law, consumer law and other legislation may all affect the enforceability and interpretation of licence terms.
Open-source and free-software licences take a different approach by granting specified freedoms to use, inspect, modify and redistribute software. The Open Source Definition and Free Software Definition describe related but differently formulated criteria for software freedom. Common open-source licences include the MIT License, Apache License 2.0 and GNU General Public License. These licences do not mean that the software has no copyright owner or that every use is unrestricted. Instead, they grant permissions under defined conditions. A licence can permit commercial use while still imposing obligations concerning copyright notices, attribution, source-code availability or redistribution terms.
Licences can contain both permissions and conditions. Permissions may include use, copying, modification, distribution, sublicensing or private use. Conditions can require preservation of copyright notices, inclusion of licence texts, disclosure of source code for certain forms of distribution or application of the same licence to derivative works. A licence may also contain disclaimers of warranty and limitations of liability. The distinction between a permission and a condition is important because violating a licence condition can affect the legal right to exercise the corresponding copyright permissions. The exact legal consequences depend on the licence wording and jurisdiction.
Software licences are distinct from software ownership and software distribution models. Buying software does not necessarily transfer copyright ownership. Downloading software does not necessarily mean that unrestricted copying is permitted. Conversely, software being available at no monetary cost does not necessarily mean it is open source or freely redistributable. "Freeware" generally describes software supplied without a purchase price but does not itself grant the rights associated with free or open-source software. "Open source" concerns the licence and associated rights, not simply whether software can be downloaded for free.
Licensing also matters when software incorporates third-party components. A project can contain dependencies distributed under different licences, each of which may impose different obligations. Developers need to identify component licences and determine whether their intended use and distribution comply with them. Copyright notices, attribution requirements and source-code obligations may need to be preserved. Software distribution can therefore involve a licence stack in which the project's own licence interacts with licences covering libraries, frameworks, fonts, images and other included material. Automated software composition analysis and dependency-management tools are often used to identify these components and associated licensing requirements.
Some licences permit modification but impose requirements on redistributed versions, while others allow modification and redistribution under very broad terms. Copyleft licences are designed to preserve specified user freedoms in derivative distributions by requiring particular licensing conditions when covered derivative works are distributed. Permissive licences generally impose fewer conditions on downstream redistribution. These differences can be important when combining components because licence compatibility is not simply a matter of whether each individual licence allows modification. The terms governing redistribution and derivative works can interact in complex ways, so organisations may conduct legal and technical licence reviews for significant projects.
A software licence is therefore a central mechanism for defining the legal permissions surrounding software. It answers questions such as who may use the software, whether it may be copied or modified, whether modified versions may be distributed and what conditions apply to redistribution. The licence should be read rather than inferred from the software's price, source-code availability or distribution channel. For developers and users, understanding licensing helps prevent accidental copyright infringement, clarifies reuse rights and establishes obligations when incorporating or distributing software. For open-source projects in particular, the licence is a fundamental part of the project's legal and practical identity.
