A Quick Guide to Common Open Source Licensing

This article is mostly general and can apply to all of ElixirNode’s services. If you are a VPS user, a majority of the software you are using from your website down to the Operating System itself is Free Libre Open Source Software (FLOSS), Minecraft Server software such as Spigot, Paper, and Magma are also Open Source along with many of your favorite plugins. The CMS or other software you may use on our Web Hosting will likely be licensed under an open source license. It is best to know these so you know what you can and cannot do and while it may not affect you directly now it may in the future especially if you want to become a developer or modify the programs you use. The world of Free Open Source Software can be complicated when it comes to licensing. There are many software licenses to permissive to strong “copyleft”. This article will quickly go over some of the most commonly used licenses, please be aware this is not legal advice and is more of a quick reference.

Permissive Licenses

A great majority of Open Source software uses a Permissive license which is why I put it first. Permissive licenses have little to no restrictions and you can often do what you please with the code and software. Here you will find the Apache, BSD, and MIT license.

Apache License Version 2

Apache License

This is a very commonly used Open Source license by the Apache Software Foundation (ASF). All of the software the ASF create including the widely used Apache Web Server use this license. Many large companies who create Open Source software such as Google use this license for their public programs and web frameworks. The Apache license is considered permissive because it allows you to use the code in any application under any license even closed source (proprietary) as long give attribution (credit) to the authors in some way. This is usually done in a file or web page called “Open Source”. The only restrictions are that you cannot use the name of the original software if you create a fork or reuse or resell the program as well as no warranty. This license also allows you to use any patents involved with the program. One of my favorite programs, SoftEther VPN uses this license. Finally, it is recognized/approved by both the FSF and OSI. Here is a link to the full license

BSD License

Free BSD Logo

This is another permissive open source license which is a lot like the Apache. It is used mostly by the FreeBSD Foundation and Apple. Like the Apache license you must include the original copyright notice and disclaimer if you are distributing the source code and/or just a binary. In the case of the 3-Clause license you are not allowed to use the original software name or contributors to endorse the software much like the Apache License version 2. There is also the old BSD 4-Clause license which just elaborates more on the 3rd Clause in the 3-Clause license which today is no longer needed. Also note unless otherwise stated, there is no warranty with this license.Here is a link to full text of the mostly used BSD 3-Caluse. If using the 2-Clause version just remove the 3rd item on the list from the file. This license is recognized/approved by both the FSF and OSI.

MIT License

MIT Logo

This is the most popular permissive Open Source license and is the most popular license used on GitHub. This license was created and used by the Massachusetts Institute of Technology back when Open Source was becoming a big deal. The MIT License like the Apache and BSD is very permissive and is used by large companies like Google, Apple, Microsoft, and beyond. A popular program in the game server hosting world that is MIT licensed is Pterodactyl. The MIT license is very simple and states that you must state the original copyright somewhere in the program like the credits and there is no warranty. Its a very small and compact license only consisting of less than three paragraphs and it is one of my personal favorites! This license is recognized/approved by both the FSF and OSI.

Other Permissive Licenses –
There are many other permissive open source licenses such as the ISC License by the Internet Systems Consortium and the GNU All-Permissive License from the Free Software Foundation, The CC and CC-BY from Creative Commons the Apple Open Source License from Apple and good ol’ Public Domain can be used but they are all extremely similar but are not as common.

Weak-Copyleft Licenses

There are a few commonly used Weak-Copyleft licenses out there. They are used by companies who make Open Source Software and want to ensure that their code stays open while still allowing it to be used in other programs. Copyleft is the Free Software Foundation’s term for a program or other piece of work that is licensed using a Free license like General Public License. Here you will find the GNU LGPL and Mozilla Public License.

GNU Lesser General Public License Version 2/3


The GNU LGPL, fully known as the GNU Lesser Public License or the GNU Libaray Public License published by the Free Software Foundation is used mostly for software libraries to allow programmers to link LGPL code into their non-(L)GPL programs. To copyleft standards this is considered permissive and the Free Software Foundation does not endorse using this license because of that. According to the LGPL you must open-source the LGPL code if you modify it with your distributed program and the software libraries must be replaceable (dynamically linked) to the program. Besides that one difference it is the same as any other GPL license. This license is recognized/approved by both the FSF and OSI. Here is a link to the full LGPLv3 license.

Mozilla Public License Version 2.0

Mozilla Logo

The Mozilla Public License or MPL for short is much like the LGPL but a little more permissive. While you must open source (disclose) all modified code with your distributed program and include a copy or give instructions on how to get a copy of the original MPL licensed files it allows to be statically linked with programs under a different license. This truly puts the MPL in the middle of permissive and copyleft. In my opinion this is the absolute best of both worlds license and should be used by more applications and software. This license is recognized/approved by both the FSF and OSI. Here is a link to the full Mozilla Public License Version 2.0

Common Development and Distribution License 1.0

Oracle Logo

The Common Development and Distribution License is a License by Oracle. It is a lot like the MPL and has the same rules. It is most known for being the license used for the OpenZFS file system. Recently there has been some controversy because the CDDL is not GPL compatible and therefore cannot become a part of the Linux Kernel. What makes the CDDL different from the MPL is that you do not need to distribute/give instruction on how to obtain the original code. This license is recognized/approved by both the FSF and OSI. Here is a link to the full Common Development and Distribution License 1.0

Copyleft Licenses

The term Copyleft is from the Free Software Foundation (FSF) and it is basically a word that means using copyright laws to enforce users rights to use, modify, and distribute the program as they please while disallowing someone to withhold those rights. Here is where you will find the GPL and AGPL.

GNU General Public License Version 2/3

GNU GPLv3 Logo

The GNU General Public License or GPL for short is the Free Software Foundation’s flagship license. It is widely used across the software world. A great majority of GNU/Linux is GPL with the Linux Kernel being licensed under the GPLv2. The GNU GPL is a strong copyleft license requiring all code linked to be also licensed under the GPL license and if you distribute your program you must follow all of the rules of the GNU GPL such as disclosing the source and enforcing user rights. The version 3 also has more restrictions such the distributor being required to provide installation documentation. The GPLv3 is also comparable with more licenses compared to older versions of the GPL. The GPL is the best license to use if you are building a desktop application and it is the license that is most used for software found on your VPS. There are a lot of rules to follow with the GPL and you can find a copy of the GPLv3 here. This license is recognized/approved by both the FSF and OSI.

GNU Affero General Public License Version 3


GNU Affero General Public License Version 3 is the newest license in the GPL family and is personally my least favorite since it is a pain to comply with at times. The AGPL is essentially the GPLv3 with one added rule, and that is if your provide a Software as a Service (SaaS) on your server and you modify the code you must disclose it and follow the same rules as the GPLv3 even if you are not directly distributing the software in binary form. The AGPL is found in many popular web applications such as Nextcloud and Libretime. Most of the time the AGPL is used for community editions of software that is dual-licensed. The AGPL is as copyleft as it gets when it comes to open source and is truly the complete opposite of the MIT license. Overall it isn’t a awful license and it serves its very specific and kind of unnecessary purpose well. Overall I would not recommend this license under any circumstances unless you really feel like it is necessary. If you are a developer looking to use code you should absolutely not touch anything with the AGPL even with a 10 foot pole. There are a lot of rules to follow with the AGPL and you can find a copy of the AGPLv3 here. This license is recognized/approved by both the FSF and OSI.

Source Available Licenses

Source Available licenses are rarely used and personally I can only think of one program that uses one and that is Pritunl VPN. The License gives no rights to the user to modify, distribute, or re-use the code in any way and it can barley be called Open Source and in my opinion makes the AGPL look like a great license. If you are just going to make your software Source-Available without being licensed under a OSI or FSF approved license then you might as well not publicly open source it at all and definitely shouldn’t use it as a selling point. If you come across a program like this you are better off forgetting about it and looking for an alternative. To see an example of a Source Available License here is Pritunl’s.

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