What is the Open Source License
There are always some people who take "open source" as the "free items, I can use it as much as I want without restriction". Free software was the mainstream at the beginning of the birth of open source. But when we look back at the history of open source development, we will find that there is a big leap between free software and open source movement, the former is more of a spirit of advocacy, while the latter focuses on the collaborative open software, so there will be very strict open source license rules and restrictions. That is because those rules that follow the spirit of open source, can open source software get healthy development. One of the carriers of the open source spirit is the open source license.
First of all, it should be clear that the copyright of the source code of open source software has neither been abandoned nor expired. Its modification, distribution, and other permissions are still subject to copyright law or open source software license. The purpose of an open source license is to regulate the use or distribution of copyrighted software.
Common Open Source License
Common open source licenses mainly include Apache, MIT, BSD, GPL, LGPL, MPL, SSPL, etc, which can be roughly divided into two categories: permissive free software licenses and copyleft licenses.
Permissive free software license is a type of free software license agreement with minimal restrictions on how the software can be used, modified, and distributed. This type of software license agreement will not guarantee that a derivative work will continue to maintain exactly the same restrictions as the original work, thus providing greater freedom of use, modification, and distribution of the original work.
However, the Copyleft License is for free use, modification, and distribution in a limited space, and must not violate the restrictive terms of the original work. If the software with a Copyleft License states that it shall not be used for commercial purposes and shall not be closed source, the subsequent derivative software must also comply with the terms.
The major difference between the two is that the Copyleft License still mandates the disclosure of the source code (derivative software needs to be open source), while the Permissive free software license does not require the disclosure of the source code (derivative software can be proprietary). Among them, Apache, MIT, and BSD are all permissive free software licenses, GPL is a typical copyleft license, and LGPL and MPL are weak copyleft licenses. SSPL is a new license created by MongoDB in recent years. SSPL is a new license created by MongoDB in recent years. There is a lot of controversies about SSPL. OSI, the Open Source Initiative, has even argued that SSPL is not an open source license agreement. In addition, there is a category of Creative Commons (CC). Strictly speaking, this agreement is not really an open source license, and most of them are used in design projects. There are a variety of CC agreements, each of which grants specific rights. Most of the strict CC agreements state an "Attribution, Non-Commercial Use, No Derivative Works" clause, which means that you are free to share the work, but you cannot change it and charge for it, and you must claim ownership of the work. This license agreement is very useful in that it allows you to distribute your work, yet retain partial or complete control over the use of the work. The least restrictive type of CC agreement is the "Attribution" agreement, which means that people can use your work however they want as long as they can preserve your reputation.
FSF and OSI
As you can see, there is a huge difference between the different licenses. You may be confused as to what the purpose of making it so complicated is. This has to start from the history of open source. The word "open source" actually originally referred to "open source software" (OSS). Open source software is computer software whose source code is freely available, and anyone can view, modify, and distribute the code. There are 2 factions in the field of open source: FSF (Free Software Foundation) and OSI (Open Source Initiative), which have different ideas about open source. FSF and OSI are non-profit organizations that promote and maintain open source order, protecting the submission, discussion and review of major open source software licenses. As long as the terms are reviewed and approved as meeting the definition of open source, they can be called open source license terms, software licensed under open source terms is known as open source software. If a commercial product contains OSS, the packaging can be marked with the OSI seal of approval, so that consumers who recognize the seal will know that OSS is used in the product and purchase the product because of its unique benefits.
Introduction to Common Open Source Licenses
Apache: Apache License is a free software license issued by the Apache Software Foundation and originally written for the Apache http server. The Apache License requires licensees to retain copyright and disclaim rights, but it is not an anti-copyright license.
MIT: The name of the MIT License comes from the Massachusetts Institute of Technology (MIT), also known as "X License" or "X11 License". The MIT is similar to the 3-clause BSD license, but endows the software licensee greater rights and fewer restrictions.
BSD: The BSD license (Berkeley Software Distribution license) is one of the most widely used licenses in free software. BSD licenses are more lenient and even closer to the Public Domain. In fact, the BSD license is considered a copycenter (intermediate copyright), somewhere between the standard copyright and the GPL copyleft.
GPL: GPL allows the code to be open source/free used and referenced/modified, and the derivative code to be open source/free used, but does not allow the modified and derived code to be distributed and sold as closed source commercial software.
Elastic License: The Elastic License is a non-commercial license with the core provision that a commercial license is required if the product is used as a SaaS.
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