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Intellectual property law gives creators rights over things they make. Source code is protected by copyright as soon as it is written, in most countries without any registration, so by default nobody else may copy or redistribute it without permission. A software license is the permission: it states what others may do with the code and on what conditions. Open-source licenses grant broad rights to use, study, change and share code, and they differ mainly in whether modified versions must stay open.
Have students find the LICENSE file in three real open-source projects and summarize, in one sentence each, what they may and may not do. Compare a permissive license (MIT) and a copyleft license (GNU GPL) on the same scenario: "I modify this library and sell my app." Discuss everyday cases such as copying a code snippet from a forum, using images in an app, and the difference between plagiarism (a matter of honest credit) and copyright infringement (a matter of permission).
When you write a program, you create something the law treats as property, even though you cannot touch it. Intellectual property is the general name for these rights. Three kinds matter most in computing. Copyright protects original creative expression, including source code, documentation, images and music. Patents protect certain new inventions, and some software-related inventions can be patented. Trademarks protect names and logos, such as a product's brand.
Copyright is the one programmers meet daily. In most countries it applies automatically the moment work is created, with no form to file. By default, the copyright holder alone may copy, change and distribute the work. Copyright covers the specific expression, not the idea. Two people can write separate code for the same algorithm, and neither copies the other.
Because the default is "all rights reserved", sharing code needs a license: a statement from the copyright holder granting permission on stated terms. When you see a `LICENSE` file in a project, that file is what lets you use the code at all.
Open-source licenses grant everyone the right to use, study, modify and share the code. They fall into two broad groups. Permissive licenses, such as MIT, BSD and Apache 2.0, ask for little beyond keeping the copyright notice, and they allow the code to be used inside closed-source products. Copyleft licenses, such as the GNU GPL, add a condition: if you distribute a modified version, you must release its source code under the same license. Many large projects, including the Linux kernel, use the GPL.
For non-software works, Creative Commons offers standard licenses built from simple conditions. "BY" requires credit, "SA" requires sharing adaptations under the same terms, "NC" forbids commercial use, and "ND" forbids changes. A photo marked CC BY may be reused in your app as long as you credit the photographer.
Two distinctions prevent common mistakes. First, visible is not the same as licensed: code on a public website still belongs to its author. Second, credit is not the same as permission. Citing a source avoids plagiarism, which is about honesty, but it does not grant the legal right to copy. Some countries allow limited uses without permission, such as fair use in the United States, but those exceptions depend on the details of each case.
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