Categories of Open Source Licenses

Open source licenses can be divided into two primary categories: Permissive and Copyleft.

The primary differences

The primary differences between copyleft and permissive licenses are compliance requirements and how “open” any code modifications must be.

In general, permissive licenses only require users to include a copy of the license text and the original copyright notice in any redistribution of the licensed code.
For example, a developer can take the code, modify it to create a new program, then keep the code of that program to themselves, making it proprietary and closed-source. They could then sell that program commercially.

Copyleft licenses have more stringent conditions.
They generally require users to include the original copyright notice and the license text, but they also obligate users to make the source code of any modifications or derivative works to all recipients of the binary, under the same license as the original.

The most popular licenses:

Approved Open Licenses.