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Permissive and copyleft licenses
(Based on materials from ORCRO)
Permissive licences have simple requirements – to credit original work, describe changes, provide
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a disclaimer, etc. Copyleft licences (“reciprocal”, “protective”, “restrictive”, derogatory: “viral”) require the rights to be preserved in derivative works
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. If you use any components (libraries) with copyleft, you are obliged to make derived source code available, which may include the entire product/project!
- Permissive – do anything
- MIT – short and simple
- ISC (OpenBSD) – further shortened equivalent
- BSD – some versions require to include the disclaimer
- Apache 2.0 – requires notice of changes, grants licence to patents unless litigating and mentions preservation of trademark rights
- Weak copyleft – file (library) scope
- MPL 2.0 – simple, allows static linking and licence variants with additional terms
- LGPL 2.1 – cleaned text of LGPL 2.0, allows dynamic linking without enforcing copyleft
- LGPL 3.0 – grants use of patents; the end-user must be able to install a modified version – it prohibits closed devices, DRM or hardware encryption or patents retaliation; compatible with Apache2.0
- Strong copyleft – project scope
- GPL 2.0 – often used
- GPL 3.0 – grants use of patents, the end-user must be able to install modified software, compatible with Apache2.0
- AGPL 3.0 (Affero) – network protective: external use of modified(!) code requires its availability – network use is a distribution of the software, modified source code must be available
- Proprietary – typically restrict user rights and protect commercial interests of copyright owners
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