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Free software licenses, definitions, types and compatibility

Posted by Pablo Gonzalez on January 8th 2013

In this article we will continue with free software licenses, definitions, types and compatibility.

Therefore, we will initially treat several definitions and subsequent years of introduction:

- Freeware: These are free programs that are usually distributed compiled. If we want to redistribute such software usually must ask the author permission. This type of software is used for propaganda in other software with more features and usually pay.

- Shareware: It is a method where the program distribution may be limited in function of a time period. Payment is usually done because these programs have propaganda, limited functions, etc ...

- Public Domain: The author waives his rights and give them to mankind. By default, a program that does not specify anything in the public domain, therefore, must be expressly stated in the software.

- Permissive licenses: Non-copyleft license that allows distributing the software under another license. Could even distributed under a proprietary license. Example, BSD.

- Licenses robust (copyleft): The license requires that the modifications are distributed free. Example, GPL.

It is important to examine and verify the licenses are not mutually incompatible. For example, a program that blends a license GPLv3 GPLv2 with inconsistent because GPLv3 violate Article 6 of GPLv2 as this does not allow adding more restrictions. If we use the GPLv3 add the restriction to provide information on facilities. From this it generates a mismatch.

Keep in mind that we want to license our software, as it will be compatible or not with other changes becoming more difficult in the future.

As a personal opinion, nowadays, prefer permissive licenses that allow even a modification under a proprietary license. This I consider a paradox, since the warrant permissive freedoms of all (even those who want to make it exclusive), but on the other band, each eliminates proprietary license and freedoms goes against keeping them.

Nevertheless, I think it is best that everyone can choose what they want to do with their freedom.

NOTE: The Linux project is generated GPLv2 licensed. The use of DRM systems can implement GPLv3 * restricting modifications to the program code not authorized by the hardware. What will happen to our open source software is not signed by the hardware? Decide yourself ...

* They are mechanisms or rights management technology to protect digital copyrights.

Now remember the freedoms 4:

a) The freedom to run the program for any purpose.

b) freedom to study the program, modify it as needed. We need access to the source code.

c) freedom to distribute copies of the program.

d) freedom to improve the program and launch it. We need access to the source code.


- The type of software Freeware grants users access to the source code and allows modification and study. True or false?

- The free software licenses allowed to be redistributed as proprietary software? True or false?

- Imagine a program with modified GPL license, do requires us to distribute the modified source code?

- Why is the original BSD license 4 clauses incompatible with the BSD GPLv2 but 3 clauses if it is compatible?

In the following article we will see some more examples of dual licensing software, discuss project management models and some exercises and examples.

I hope you find it useful.

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