What is a license

GNU General Public License

The GNU General Public License (GPL) is probably the most commonly used license for open source projects. The GPL grants and guarantees broad rights to developers of open source projects. Basically, it allows users to legally copy, distribute and modify software. This means you can:

* Copy software

Copy software to your own server, client's server, your own computer, almost anywhere you want, and there's no limit to how many.
* Publish software

Publish the software you want, for example, provide download links on your website, burn it into CD, print it out, and so on.
* Charge a fee

if you want to charge someone when you provide the software, such as when setting it up on someone else's website or for other purposes. The GPL allows you to do this, but you have to give your customers a copy of the GPL, telling them they can get a free version elsewhere. Of course it is best to tell the client why you are charging before that.
* Can be modified arbitrarily

If you want to add or remove features, no problem. If you want to use parts of the code in other projects, it's also possible, but the only restriction is that this project must also be released under the GPL.

Commercial software cannot use GPL-licensed code.
The GNU Lesser General Public License

has another GNU License: the GNU Lesser General Public License (LGPL). It grants fewer permissions than the GPL. In general, LGPL is more suitable for linking to non-GPL or non-open source library files. Due to the provisions of the GPL, software that uses part of the GPL code must also use the GPL, and developers cannot use the GPL to develop paid software or proprietary software. LGPL does not have this requirement, and does not require the use of the same license as part of the code.

Commercial software can be used, but cannot modify the code under the LGPL agreement.
BSD License

BSD License has fewer restrictions than other free software licenses, such as GPL. But please note the difference between the two versions of the BSD License: New BSD License/Modified BSD License and Simplified BSD License/FreeBSD License. Both of them are GPL-compatible free software licenses.

The New BSD License ("3-clause license") can be used for any purpose as a disclaimer of copyright notices and warranty licenses, and can be maintained through redistribution of unlimited length, that is, if the redistributed product contains source code , the source code must have the BSD protocol in the original code. It also has a special restriction clause, which restricts the use of the worker's name of the derived work without a special license, which means that the author/organization name of the open source code and the name of the original product cannot be used for marketing purposes.

The main difference between the New BSD License and the Simplified BSD License is that the latter ignores the non-approval clause.

Commercial software can be used or modified code using the BSD license.
MIT License

MIT is a permissive license agreement like BSD, the author just wants to keep the copyright without any other restrictions. That is, you must include the original license statement in your distribution, no matter if you distribute it as a binary is still released as source code.

* You can use, copy and modify the software
* You can use the software for free or sell it
* The only restriction is that it must be accompanied by the MIT license.

Commercial software can be used, you can modify the code of the MIT license, and you can even sell the MIT license. code.
Mozilla Public License 1.1 (MPL)

The MPL agreement allows free redistribution and free modification, but requires that the copyright of the modified code belongs to the originator of the software. This kind of authorization protects the interests of commercial software, and it requires a free contribution of copyright to the software based on such software modifications. In this way, the copyright of all code surrounding the software is concentrated in the hands of the originating developer. But MPL is allowed to be modified and used for free. MPL software has no requirements for linking.

Commercial software can use or modify the code of the MPL protocol, but the copyright of the modified code belongs to the initiator of the software.
Common Development and Distribution License

CDDL (Common Development and Distribution License) open source agreement, is an extension of MPL (Mozilla Public License), it allows public copyright use, no patent fees, and provides patent protection, can be integrated In commercial software, self-publishing licenses are allowed.

Commercial software can use or modify the code of the CDDL protocol.
Apache License

Apache Licence is a protocol adopted by Apache, a well-known non-profit open source organization. Similar to BSD, the agreement also encourages code sharing and respects the original author's copyright, and also allows code modification and redistribution (as open source or commercial software). Conditions that need to be met:

* An Apache License needs to be given to users of the code.
* If you modify the code, it needs to be explained in the modified file.
* In the extended code (modified and derived from the source code) the license, trademarks, patent notices and other clarifications specified by the original author need to be included in the original code.
* If the redistributed product contains a Notice file, the Apache License must be included in the Notice file. You can add your own license to the Notice, but it cannot appear to constitute a change to the Apache License.

Apache Licence is also a commercial application friendly license. Users can also modify the code when needed to meet their needs and release/sell as an open source or commercial product.

Commercial software can be used or modified to use the Apache protocol code.
Eclipse Public License

The EPL is a license similar to the CPL, and any code that extends from the Eclipse source code must also be open source.
Creative Commons

Creative Commons (CC) licenses are less open source licenses, and they are often used for design projects. The CC license has broad definitions, each of which grants certain rights. It has four basic parts that can be used individually or in combination. Here's a partial overview:

* The attribution

author must be the original author of the work. Otherwise, the work may be modified, distributed, reproduced and otherwise used.
*Share Alike

Work can be modified, distributed, etc., but must be under a license.
*Non-Commercial

Can be modified, distributed, etc., but not used for commercial purposes. There is a bit of ambiguity about what is "commercial" (no clear definition is provided), so you may need to clarify this in your own projects.
* No Modification

This means that you may copy and distribute the licensed work, but you may not modify it in any way, or develop on the original basis.

The use of commercial software must comply with the specific provisions of the CC agreement, and the strictest license will be the authorization of "attribution, non-commercial, and cannot be modified". This means that you are free to share work, but you cannot change it, you must give credit to the original creator.
Common Public License 1.0

Common license has some detailed provisions worth referring to:

* Clarified the patent authorization. In general open source software, it is clear that the copyright owner of the source code licenses his copyright rights such as the right to modify and copy to the public, but retains the right of authorship. On this basis, the Common license also clarifies that if the source code contains patent rights, the source code The patentee of the code licenses the exclusive right of reproduction and use to the public.
* Provides that source code and modified source code may be combined with other types of code not subject to this license and released as a new product, as long as the source code and modified source code obtained under this license can be Release as required by that license.
* Refines the circumstances under which this license is terminated, including the occurrence of a patent infringement lawsuit.
* A principle of independent responsibility is clarified, that is, if the user who uses the source code according to the license applies the obtained source code to commercial use, then he will be responsible for the use of the source code program that appears in the commercial application. The resulting infringement lawsuit bears full responsibility. This provision is rather special, and is not required by most open source software licenses.

Commercial software can use or modify the code of the Common agreement, but it shall bear the infringement liability arising from the code.