Open source licenses: Everything you need to know

Open source technology makes the world round, shapes it as much as 90% Through the modern software stack Structure; Library; database; operating system; and countless Standalone application.

The benefits of open source software are well understood, promising greater control and transparency However, there is one A perennial struggle Between open source and proprietary areas, many companies lead the way Retreat from open source To protect their commercial interests. At the heart of all this is the thorny issue of licensing.

There are two broad types of licenses that meet formal open source definition As determined by the Open Source Initiative (OSI) “Permissive” licenses carry few restrictions in terms of how users can modify and distribute the software, making it popular with companies wishing to use it commercially. And then there’s the “copyleft” license, which provides similar freedoms but with a significant caveat: any modified version of the software must also be distributed under the same original copyleft license. This is not so attractive to businesses wishing to protect their proprietary work.

But there’s more to it than that, with different licenses existing within each bucket. Additionally, there are numerous licenses that, while not strictly open source, are worth knowing about.

permissive

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Appropriately named, originating at the Massachusetts Institute of Technology in the 1980s with The license is the most popular open source license, sitting on most metrics top spot in the GitHub development community for many years.

Used by projects including response (front-end JavaScript library) and ruby (general purpose programming language), the MIT license allows developers to use the software however they like. As with most such licenses, it is provided without warranty, meaning that the authors are released from any liability (such as data loss) resulting from damage caused by their software. All developers must consider the original copyright notice and MIT license in any derivative work.

But the MIT license has a drawback: it does not expressly grant patent rights. This means that if a given piece of software relies on patented technology, it can create legal uncertainty for developers who deploy the software without obtaining separate permission for said patented technology.

However, this underscores one of the key selling points of the MIT license: just that 200 wordsThe language is simple and concise. Muddying things with vague, word-soup patent spiel will add unnecessary complexity to projects that are unlikely to be patent-related, such as high-level programming languages ​​or web frameworks.

But many open source projects intersect with patented technology, such as hardware-centric software like Android.

Apache License 2.0

Published by the Apache Software Foundation Apache License 2.0 In 2004, an update to an earlier license included an express patent grant to protect users from lawsuits So, for example, if a developer contributes a unique image processing algorithm to a project licensed under Apache 2.0, any patents the developer holds on that algorithm are automatically licensed to all users of the software.

Most people will be familiar with Google’s brand of Android, complete with the App Store and homegrown suite of tools and services. But the underlying Android Open Source Project (AOSP) is notably available under the Apache 2.0 license, a Deliberate action by Google In 2008 to counter Apple and encourage phone makers to use Android other proprietary incumbents at the time (such as Symbian). And it worked. Samsung, HTC, LG, and the rest have jumped on Android.

A byproduct of this, however, is the Apache License around 2.0 Five times the number of words Due to the patent grant text, among other additions and clarifications is that of MIT. But that’s the trade-off, and it illustrates the key differences between the two most commonly permitted open source licenses

Other Permissive Licenses

BSD 2-Clause License Similar to MIT, but with key differences in the language used. For example, it specifies that a copy of the license should be included with both source code and compiled binary form. And then there’s BSD 3-Clause Licensewhich contains an additional “no authorization” clause that restricts the use of the names of copyright holders and contributors for promotional purposes in any derivative project.

There is also MIT No Attribution License (MIT-0), which is simpler than MIT, does not require attribution to derivative software. It’s close to putting software in the public domain to use, the author doesn’t retain copyright and the ability to change things in the future.

Copyleft

GNU General Public License (GPL) v. 2.0 and 3.0

Free Software Foundation (FSF) published the GNU General Public License (GPL) in 1989 and was one of the first copyleft licenses for general use.

Copyleft licenses are often appropriate for projects that require input from the community, versus projects supported by a single corporate entity. By requiring all modifications to be available under the same open source license, it reassures contributors that their hard work won’t be used in proprietary software without benefiting the larger community — in theory, at least, it can be difficult to discover every violation and then enforce the terms of the license.

Launched in 2007, GPL 3.0 The third most popular license, According to GitHub data. The license introduced significant updates GPL 2.0Including patent grant provisions and improved compatibility with other open source licenses. It also prohibits what is known as “Tivoization”, where hardware manufacturers benefit from GPL-licensed software using digital rights management (DRM) methods to prevent users from installing modified versions of that software.

Notable GPL adopters include WordPress, which is available under a GPL 2.0 “or later” license, leaving it up to the developer to decide which modifications they distribute under which license.

Linux, for its part, is one of the most successful open source projects of all time, used in servers, cloud infrastructure, embedded systems, and even Android. However, the underlying Linux kernel is only available under a GPL 2.0 license, granted Linux creator Linus Torvalds is against some provisions Added in version 3.0 of the license — including the tivization clause.

Released under the GNU General Public License (AGPL) 3.0

Afero General Public License (AGPL) like GPL 3.0, is a “strong” copyleft license that promotes software freedom and ensures that modified versions remain open source. However, a key difference with the AGPL is that it focuses on web-based services and applications, where the software is run from a server rather than distributed as an executable file.

Under a GPL 3.0 license, developers of software such as SaaS applications do not have to disclose the source code for modified software if it is run over a network. The AGPL license closes this loophole, requiring third parties to make source code available even if the modified software is running from only one server.

Released in 2007 by the Free Software Foundation, the AGPL 3.0 license grew in popularity due to the rise of cloud computing and SaaS, and today it The fifth most popular open source license.

GNU Lesser General Public License (LGPL)

Also a product of the Free Software Foundation GNU Lesser General Public License (LGPL) is a “weaker” copyleft license, as it is more business-friendly with less strict terms on sharing. The LGPL is typically used for software libraries where project authors want to encourage contributions from the community, but it also allows proprietary software to link to the library without having to open source their entire proprietary code. If someone modifies the open source library itself, they only need to release those modifications under the LGPL license.

Mozilla Public License 2.0

Published by Mozilla Foundation in 2012 Mozilla Public License (MPL) 2.0 is the tenth most popular open source license today GitHub’s license metrics. The MPL is a weak copyleft license designed to protect proprietary code while enabling developers to benefit from open source software.

While LGPL focuses on the library level and GPL on the project level, MPL works on an individual file level that requires the user to share a narrower set of code.

Public Domain and Creative Commons

Although an “open source license” grants certain rights, there are always conditions attached. Those who wish to place their software entirely in the public domain without warning, however, can do so in other ways.

Publishing software without a license is not enough; Copyright law applies by default to most creative works, including software. This is where a “public domain dedication” can help

Specially designed for software, without license The ninth most popular license on GitHub (although whether it can actually be called a “license” is debatable). Although OSI allowed As for a license in 2020, it noted that the document was “poorly drafted” and questioned its legal effectiveness in jurisdictions (such as Germany) where it is not possible to donate works to the public domain.

Without a license, like Creative Commons CC0-1.0 It is a public domain dedication tool, although it focuses more broadly on creative work. It uses clearer, more professional legal language that may be more in line with international law. It is worth noting that Creative Commons CC0-1.0 has been applied for approval As an open source compliant license in 2012, but Application withdrawn After OSI raised concerns that it expressly excluded patent grants.

There are other public offering tools, eg Zero-clause BSDwhich may appeal because its language is simpler. However, there is no consensus on the best process for granting all rights to a given piece of software.

“Wrong-pen” origin

There are countless other licensing paradigms across the software spectrum.

In some cases, businesses will release software under a Dual license modelUsers are able to choose between an accepted open source license and a commercial license depending on their purpose. Then there’s “open core,” which offers the software under an open source license, but with key features paywalled. In other cases, a company may add a Commons Clause Additions to otherwise permissible open source licenses impose commercial restrictions.

There are many licenses that look and smell like open source, but are ultimately inconsistent with the open source definition.

In 2018, Database giant MongoDB Transferring from a copyleft AGPL license to a server-side public license (SSPL), a MongoDB’s own creation license. Although SSPL is still fairly “open”, it is known as “available source” meaning that the code is accessible but has significant commercial restrictions, which is a Big no-no As far as OSI is concerned.

D The folks at MariaDB has taken a similar path with the Business Source License (BUSL), which imposes commercial restrictions before transitioning to a true open source license after a certain number of years. There is another A similar movement is underway looking to make that”legitimate source“One thing is licensing. This includes Effective source licensewhich is considered as a simpler alternative to BUSL.

you so called”Moral sources” license from time to time, viz Hippocratic licensewhich prohibits the use of software that violates internationally recognized human rights. Likewise, open standards JSON The file format has a very permissive license, except for a funny clause at the end: “The software will be used for good, not evil“