Several common open source software license agreements (GPL, LGPL, Apache License, BSD)

Gpl

The GPL grants the procedure to accept the following rights, or "freedom":

* Freedom to run this program for any purpose

* The freedom to modify the program (source code is the precondition) for the purpose of learning program working mechanism

* Re-release copy of the Freedom

* Improve this program, and publicly release the freedom of improvement (can get source code is the premise)

Conversely, the end-user license for all copyrighted software is almost never granted to the user (except for the right to use) and may even limit the behavior permitted by law, such as reverse engineering.

The main difference between the GPL and some other more "licensed" free software licenses (such as BSD licenses) is that the GPL seeks to ensure that these freedoms are protected in reproductions and derivative works. It is realized by a legal mechanism called copyleft, invented by Stallman, which requires that the derivative works of the GPL program be under the GPL. In contrast, BSD-style licenses do not prohibit derivative works from becoming copyrighted software.

The GPL does not grant unlimited rights to the licensee. The grant of redistribution is subject to the source code of the licensee's Open software and all modifications. Copies, modified versions, must be licensed under the GPL.

These requirements are copyleft, which is based on the legal copyright of the works. Because it is copyrighted, the licensee is not entitled to modify and re-distribute (except for reasonable use) unless it has a copyleft clause. If someone wants to exercise a right that is normally prohibited by law, simply agree to the terms of the GPL. Conversely, if someone publishes software that violates the GPL (such as open source code), he may be sued by the original author.

Copyleft uses copyright law to achieve its opposite purpose: Copyleft gives an inalienable right, rather than the limitations imposed by copyright law. This is why the GPL is known as the "Black copyright law".

Many GPL software publishers bundle the source code with the executable program. Another way is to provide the source code with physical media (such as a CD) as a carrier. In practice, many GPL software is published on the Internet, the source code also has a lot of FTP way to get.

Copyleft is only effective when the program is re-released. Modifications to the software may not be made public or open to source code, as long as it is not released. Note that copyleft only has effect on the software, and the output of the software is not effective (unless the software itself is output). However, this may be changed in GPL version 3.

Lgpl

The GNU wide Universal Public License, referred to as LGPL (GNU Lesser General publicly License), is used in some (but not all) GNU libraries. This license was formerly known as the GNU Library general Public License.

LGPL is a variant of the GPL, and it is the GNU's offer to get more support from even commercial software developers. The biggest difference from the GPL is that free software, which can be privately used by LGPL, can be privately owned without the need for free software. Therefore, any company should ensure that it is licensed under LGPL or other GPL variants before using free software.

Apache License

Apache License is the protocol used by the famous non-profit open source organization Apache. The agreement is similar to BSD, encouraging code sharing and respecting the authorship of the original author, as well as allowing the code to be modified and republished (as open source or commercial software). Conditions that need to be met:

* Need to give code to users a copy of Apache License

* If you modify the code, you need to modify the file to describe

* In the extended code (modified and in code derived from the source code) need to have the original code of the Agreement, trademarks, patent statements and other original author requirements to include the instructions

* If a re-released product contains a notice file, the Apache License is required in the notice file. You can add your own permission to the notice, but you may not be able to represent changes to Apache license

Apache License is also a friendly license for commercial applications. Users can also modify the code as needed to meet their needs and publish/sell as open source or commercial products.

Bsd

The BSD Licensing license (FreeBSD Copyright information) has a variety of licensing licenses. In general you can handle the software arbitrarily, as long as you indicate in the software that it is from the project. That means you have greater freedom to dispose of software. If you make changes to the software, you can limit the freedom of other users to get the software you have modified.

The BSD licensing license does not realize the "permeability" freedom, which means that it does not guarantee the continuity of the Open software source code. So if you want to use BSD software developed by someone else, make some changes, sell it as a product, or just keep a secret of what you do besides software development, then you can profit from it.

When a non-programmer simply understands the functionality of a program, but does not know how it is done, even if you do not do any work in the development software, you can sell the software to the user through superb marketing techniques. With the most popular desktop operating system as an example, you can get a good understanding of a software company that has no good program skills and can sell it to its customers as long as it has a superb marketing strategy. If you do not have strong programming skills, but have a strong market capability and can include other developers ' software into their own systems, while not opening their own changes will be very powerful ability. From a business point of view, if you use a BSD licensed software, you can do it any way you like. You can better control your OS system and prevent others from copying your commercial products.

Summarize

Simply put, you use the GPL license software, then your software products are "infected" by the GPL, you must also be "free"! This is hard for domestic business software developers to accept.

But LGPL, Apache License, BSD does not exist this problem, the latter two only require you to the software of the original author of the work of the necessary recognition and respect on the line, so this is suitable for commercial applications.

So when you choose to apply open source software, be sure to understand your use, select the appropriate license software.

Finally, we can refer to the GPL's comments:

Steve Ballmer, chief executive of Microsoft in 2001, called Linux "cancer" because of the GPL's impact. Microsoft's criticism points out that the real reason Microsoft hates the GPL is that it is counterproductive to Microsoft's "encirclement, expansion, and elimination" strategy. Note Microsoft has released some of the components contained in SFU (Microsoft Windows Services for UNIX) under the GPL, such as GCC.

The GPL's critics often believe that the GPL is a "contagious" virus, because the GPL clause stipulates that the derivative works must also be GPL. Since "deductive works" are often interpreted as software that contains GPL code or is dynamically linked to the GPL library (as above), the "virus" is derived from the GPL's requirement for compulsory inheritance of licenses. This is the difference in philosophy between the GPL and the BSD-type license. Supporters of the GPL believe that free software should ensure that its derivative works are equally "free", but others believe that free software should give users the greatest freedom

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Several common open source software license agreements (GPL, LGPL, Apache License, BSD)