The MIT License is a short, permissive open-source license. It allows you to use, copy, modify, merge, publish, distribute, sublicense, and sell the software. The only requirement is that you include the original copyright notice in your copy.
The Apache 2.0 is a modern permissive license. Like MIT, it allows full commercial use. Crucially, it includes an explicit patent grant, protecting you from patent lawsuits from the contributors.
AFL-3.0 is a permissive, OSI-approved license with a patent retaliation clause. No copyleft, no network trigger, but attribution is required.
The BSD 2-Clause License ("Simplified BSD" or "FreeBSD License") is a permissive free software license. It allows use, modification, and distribution for any purpose, including in proprietary products, with two conditions: keep the copyright notice and the warranty disclaimer.
The BSD 3-Clause License (also known as "New BSD" or "Modified BSD") is a permissive free software license. It is very similar to the MIT License, allowing you to use, modify, and distribute the software for any purpose. The key difference is an added clause that prohibits using the nam...
The ISC License is a permissive free software license functionally equivalent to MIT and BSD 2-Clause. It allows use, modification, and distribution for any purpose, including in proprietary products, with one condition: keep the copyright and permission notice.
The Mozilla Public License 2.0 (MPL-2.0) is the "middle ground" of open source licenses. It is a weak copyleft license.
The EPL-2.0 is a business-friendly, weak copyleft license. It allows for proprietary integration while ensuring that modifications to the original files remain open source.
The LGPL v2.1 is a weak-copyleft license that lets proprietary code link to an LGPL component without becoming open source. Modifications to the component itself must be shared, but there is no network clause, so self-hosting and internal network use trigger nothing.
The LGPL (Lesser General Public License) is a compromise between the permissive Apache/MIT and the strict GPL. It allows you to link your proprietary software to an LGPL library (dynamically) without forcing your proprietary code to become open source. However, if you modify the LGPL li...
The GPL v2 is the classic "Copyleft" license (Linux Kernel). It ensures that if you distribute the software, you must provide the source code. Unlike v3, it does not explicitly address "Tivoization" (locking hardware) or patent grants as aggressively.
The GPL v3 is a "Copyleft" license. It guarantees freedom for the end-user, not the developer. If you distribute software that links to GPL code, your entire application must also be released as open source under GPL.
The Affero GPL (AGPL) is designed to close the "SaaS Loophole." Unlike standard GPL, if you run AGPL software on a server and users interact with it over a network (e.g., a website), you MUST share your source code with them if you modified the software.
The European Union Public Licence is the EU's official OSI-approved copyleft licence. Its copyleft reaches network and SaaS use like the AGPL, but a compatibility clause lets combined works move to the GPL, AGPL, LGPL or MPL.
The Open Software License 3.0 (OSL-3.0) is a network copyleft license, often compared to the AGPL but with distinct legal mechanisms.
The Server Side Public License (SSPL) is not an official Open Source license. Created by MongoDB, it allows you to use the software freely, but if you offer it to others as a service, you must publish the source code of your whole service stack under the SSPL.
The Functional Source License (FSL) is a "Source Available" license: you may use, copy, modify and redistribute the code for any purpose except a Competing Use. Each version becomes available under MIT or Apache 2.0 two years after its release.
The Business Source License 1.1 (BSL or BUSL) is a "Source Available" license, NOT an Open Source license. It allows copying, modification, redistribution and non-production use; production use only as far as the licensor's Additional Use Grant permits.
The Elastic License 2.0 (ELv2) is a "Source Available" license created by Elastic. It is NOT an Open Source license by the OSI definition. It is free to use, except to provide the software to others as a hosted or managed service.
The Sustainable Use License (often associated with the "Fair Code" movement) is a "Source Available" license, not an Open Source license by the OSI definition. It grants broad rights to view, modify, and use the software for free, but only for internal business, non-commercial or personal use.
A custom license is a non-standard license a vendor writes or modifies itself, often a standard license with added clauses on branding or trademarks. Its terms have to be read one by one.