BSD licenses facts for kids

BSD licenses are like special rulebooks for computer programs. They are a type of permissive free software license, which means they let people use, change, and share software with very few rules. This is different from "copyleft" licenses, which have more rules, like requiring you to share any changes you make.

The first BSD license was used for a computer operating system called the Berkeley Software Distribution (BSD). Think of an operating system like the main program that makes your computer work, similar to Windows or macOS. Over time, the original BSD license changed, and newer versions are now called "modified BSD licenses."

BSD is both a specific license and a group of similar licenses. The modified BSD license, which is widely used today, is very much like the original one. It's a simple license that mainly asks you to keep the original license notice if you share the program's code. If you share the program in a ready-to-use form (like an app), you just need to include the notice. Unlike some other licenses, BSD licenses don't require you to share the program's source code at all.

What Are BSD Licenses?

BSD licenses are a family of rules that tell you what you can and can't do with certain computer programs. They are known for being very flexible. This means they give people a lot of freedom to use, change, and share software.

Different Kinds of BSD Licenses

Over time, several versions of the BSD license have been created. The most common one you'll see today is the 3-clause version. This version is an updated form of the first 4-clause license.

In all BSD licenses, `<year>` means the year the copyright was made. The `<copyright holder>` is usually the "Regents of the University of California," who first created these licenses.

The Original 4-Clause License

The first BSD license had a special rule called the "advertising clause." This rule said that if you used software with this license, you had to mention the original creators in any advertisements for your new product. This was the third rule in the original license.

Here's a simplified look at the main rules:

• You must keep the copyright notice and license rules if you share the original code.
• If you share the program as an app, you must include the copyright notice and rules in the documentation.
• All ads for products using this software had to mention the original creators.
• You couldn't use the creators' names to promote your product without their permission.

Many people found this advertising rule difficult. If you combined many programs, each with a different creator, you would have to list all of them in your ads. For example, in 1997, one version of NetBSD had 75 such mentions! Also, this rule didn't work well with another popular license called the GNU General Public License (GPL). The GPL doesn't allow extra rules like the advertising clause. Because of this, the Free Software Foundation, which supports free software, suggested that developers avoid using this specific 4-clause license for new projects.

The 3-Clause License (New BSD License)

The advertising rule was removed from the official BSD license on July 22, 1999. This newer version is often called the "New BSD License," "Revised BSD License," or "3-clause BSD."

This version is very popular and is approved as an "Open Source" license. The Free Software Foundation says it works well with the GNU GPL. They suggest being specific when you talk about this license to avoid confusion with the older 4-clause version.

This 3-clause license lets you share and use the software for any reason. You just need to keep the copyright notices and the part that says the software comes "as is" (meaning no guarantees). It also says you can't use the names of the people who helped create the software to promote your product without their specific permission.

The 2-Clause License (Simplified BSD License)

An even simpler version of the license is used by projects like FreeBSD. This 2-clause license is very similar to the 3-clause version, but it removes the rule about not using names for promotion.

The Free Software Foundation also says this "FreeBSD License" is compatible with the GNU GPL. Like with the 3-clause license, they suggest being clear about which specific BSD license you are talking about.

The 0-Clause License (BSD Zero Clause License)

The BSD 0-clause license is the simplest of all. It removes almost all requirements. You don't need to include the copyright notice, the license text, or the "as is" disclaimer when you share the software. This makes it very similar to putting software into the Public Domain, where anyone can do anything with it.

This license is also known as "0BSD." It was created by Rob Landley for his project Toybox because he wanted a license with even fewer rules than the GPL.

Why License Compatibility Matters

License compatibility is important because it determines if you can combine different pieces of software that have different licenses.

Using BSD Licenses in Business

The FreeBSD project believes that BSD-style licenses are great for companies. This is because they have very few rules and work well with "proprietary" licenses. Proprietary software is like a secret recipe that companies keep to themselves. BSD licenses allow companies to use the software in their own secret products. This means a company can take a BSD-licensed program, add their own special features, and then sell it as a closed-source product. This flexibility is a big advantage for businesses.

Working with Other Free Software Licenses

The 3-clause BSD license, like most "permissive" licenses, works well with almost all other FOSS (Free and Open-Source Software) licenses.

The 3-clause and 2-clause BSD licenses are approved by the Free Software Foundation as being compatible with the GPL. They are also approved as "open source" licenses. However, the original 4-clause BSD license is not compatible with the GPL because of its advertising rule.

See also

In Spanish: Licencia BSD para niños

• Comparison of free and open-source software licenses
• Software using the BSD license (category)