Apache License facts for kids

The Apache License is a special set of rules for computer programs. It's like a permission slip that tells you what you can do with software created by the Apache Software Foundation (ASF). This license is very permissive, which means it gives you a lot of freedom.

You can use the software for almost anything you want. You can also share it with others, change it, and even share your changed versions. The best part is, you don't have to pay any extra fees or royalties to use or share this software. Many projects, both from the ASF and other groups, use the Apache License for their software.

How the Apache License Started

The Apache Group, which later became the Apache Software Foundation, started releasing their Apache HTTP Server way back in 1995. Their first license was similar to an older license called the Original BSD license. It had a few rules, like making sure you didn't use the Apache name for your own changed versions.

In 1999, another group called the Berkeley Software Distribution changed their BSD license. They removed a rule that said you had to mention them in your advertising. Following this, in 2000, Apache also updated its license to Apache License 1.1. With this new version, if you changed the software, you only needed to mention Apache in your documentation, not in your ads.

Then, in January 2004, the ASF made a big change. They created the Apache License 2.0. Their goals were to make it easier for other groups to use the license. They also wanted it to work better with software that uses the GNU General Public License (GPL). This new version also made it clearer how people could contribute to the software. It also added rules about patents, which are special rights for inventions.

What the License Allows You to Do

The Apache License is very permissive. This means it's different from some other licenses, like copyleft licenses. Copyleft licenses usually require you to share any changes you make under the same license. But with the Apache License, you don't have to.

However, you still need to follow some important rules. You must keep the original copyright notices and disclaimers in the software files. If you change a file, you need to add a note saying that you made changes.

Sometimes, the original software comes with a special text file called `NOTICE`. If it does, any software you create based on it must also include a copy of this `NOTICE` file. This file usually has important information or extra credits. The `NOTICE` file doesn't change the license rules themselves. It's just for information. You can even add your own notes to it, as long as they don't try to change the license.

If you contribute your own code to a project that uses the Apache License, it's usually understood that your contributions will also follow the same license rules.

Understanding Apache License 2.0

The Apache License 2.0 has a special part in Section 3 that deals with patents. A patent is a legal right that protects an invention. This section gives you permission to use any patents that a contributor might have related to the software. This means you can make, use, sell, and share the software without worrying about their patents.

However, there's a catch. If you sue someone, claiming that the software or a part of it uses your patent without permission, then your patent permissions from the Apache License for that software are immediately canceled. This rule helps prevent lawsuits and encourages everyone to work together.

Working with Other Software Licenses

The Apache Software Foundation and the Free Software Foundation both agree that the Apache License 2.0 is a free software license. This means it gives users the freedom to use, study, share, and change the software.

They also agree that Apache License 2.0 works well with the GNU General Public License (GPL) version 3. This is important because it means you can combine code that uses the Apache License 2.0 with code that uses GPLv3. The combined software would then be licensed under GPLv3.

However, the Free Software Foundation believes that older versions of the Apache License (before 2.0) are not compatible with GPL versions 1 and 2. They also think these older Apache licenses don't work with GPLv3. Because Apache License 2.0 includes rules about patents, the Free Software Foundation often suggests using it over other similar licenses that don't have those patent rules.

See also

In Spanish: Apache License para niños

• Comparison of free and open-source software licenses
• List of Apache Software Foundation projects
• Software using the Apache license (category)