Different types of software licenses require you to meet certain obligations if you want to reuse the code. Here are 5 common types of software licenses.
If you write code, you also reuse code, including code snippets, libraries, functions, frameworks, and entire applications. All software code comes with certain rights and obligations if you want to add it to your codebase. Free and open source software (FOSS) is free of cost, but you aren’t free to use it as you wish. Even unlicensed code snippets copied from Stack Overflow have obligations for reuse. But formally developed code usually comes with a specific software license.
There are many different types of software licenses, with some requiring you to make your source code public. To protect your code, you need to understand these software licenses before using any code you didn’t write yourself.
Here are five types of common software license models you should know about. Four are examples of open source licenses (which allow you to reuse code to some extent), and one disallows any reuse whatsoever.
Public domain. This is the most permissive type of software license. It means that anyone can modify and use the software without any restrictions. But you should always make sure it’s secure before adding it to your own codebase. Note that code that doesn’t have a license is NOT automatically in the public domain.
Permissive. Permissive licenses are also known as “Apache style” or “BSD style.” They contain minimal requirements about how the software can be modified or redistributed. This type of software license is perhaps the most common and popular with free and open source software. Aside from Apache and BSD, another common variant is the MIT License.
LGPL. The GNU Lesser General Public License allows you to link to open source libraries in your software. If you simply compile or link an LGPL-licensed library with your own code, you can release your application under any license you want, even a proprietary license. But if you modify the library or copy parts of it into your code, you’ll have to release your application under similar terms as the LGPL.
Copyleft. Copyleft licenses are also known as reciprocal licenses or restrictive licenses. These licenses allow you to modify the licensed code and distribute new works based on it, as long as you distribute any new works or adaptations under the same software license. For example, a component’s license might say the work is free to use and distribute for personal use only. Any derivative you create would also be limited to personal use only. “Derivatives” includes any new software you develop that contains the component. The catch here is that any end user of your software also has the right to modify the code. Therefore, you must make your own source code available. Exposing your source code may not be in your best interests. The most common example of a copyleft or reciprocal license is the GPL.
Proprietary. Of all types of software licenses, this is the most restrictive. The idea behind it is that all rights are reserved. It’s generally used for proprietary software where the work may not be modified or redistributed.