Open source license GPL license on linux.

The most important principles of the GPL agreement are: 1. Ensure that the software is released in open source form from beginning to end to protect the development results from being stolen and used for commercial sale.

As long as any set of software uses the source program of a third-party software protected by the GPL agreement and releases it to non-developers, the software itself will automatically become an entity protected and bound by the GPL.

That said, it must be open source at this point.

2. The GPL is roughly a reflection of left copyright (Copyleft, or translated as "anti-copyright", "copyright belongs to the left", "copyright does not exist", "version responsibility", etc.).

You can remove all copyright information of the original work, as long as you keep it open source and attach the GPL license with the source code and binary version, so that future generations can clearly know the authorization information of this software.

The essence of GPL is that as long as the software is completely open source, users should be given as much room as possible to develop freely, so that the software can develop faster and better.

3. No matter what form the software is released in, the source code must be attached at the same time.

For example, if you provide a download on the Web, you must clearly provide a link to the source code download on the same page as the binary version (if available).

If distributed on CD-ROM, a CD-ROM of the source files must also be included.

4. Companies or individuals that develop or maintain software developed under the GPL protocol can charge users a certain service fee.

But it is an old saying - the complete source code of the software must be provided free of charge, and the source code must not be bundled with services or bundled in any disguised form.