licensing 101

Why license

There are numerous reaons why you should license your work:

• it allows others to do specific things with your work that you want

• it prevents others from doing specific things with your work that you do not want

• it makes the situation much clearer for everyone (especially for potential contributors)

• it's much better than writing a list of rules by your own as already existing licenses are very detailed and are legally recognized by various institutions

  What happens if I don't license my work?

All works (not just software) automatically get "All rights reversed" unless stated otherwise. This isn't inherently bad, but generally makes any sort of reuse and redistribution illegal so if you want even slightest incentive for others to make use of your work other than just looking at it, you should decide on a specific license. Note that if you publish your work somewhere (especially online), you implicitly agree to this place's rules which might immediately grant some rights for users (e.g. ability to see and copy it). More info on https://choosealicense.com/no-permission/.

If you want the opposite - maximum freedom for users with no desire to preserve specific rights as the author, you can state that you dedicate your work to the public domain and voluntarily resign from all rights.

Public domain

The public domain consists of all the creative work to which no exclusive intellectual property rights apply. Those rights may have expired, been forfeited, expressly waived, or may be inapplicable.[wiki_PD]

Almost any work sooner or later will become public domain. Various jurisdictions place different periods for different works (from 10 years to the point of author's death and many different conditions) so the situation is a bit complicated. Fortunately for vast majority of works by the time they go to the public domain all potential benefits were already gained by the author.

There is only 1 thing which you can not do with public domain work: claiming you did it. The fact who did the work is irrevocable.

Proprietary licenses

This isn't main focus of the article but it's worth to mention proprietary licenses as a contrast to all open licenses.

Such licenses are typically very restrictive:

• usually allow to obtain the work only in the final form (e.g. compiled code, raster image without layers) without access to the source (e.g. source code, vector graphics with layers and metadata)

• they limit or disallow copying

• they disallow modifications and reverse engineering

The main point of such licenses is to prevent users from using the work in ways other than the very narrow set intended by the author. The main motivation is to prevent copying, reverse engineering and other uses which can significantly harm profits of the author.

Majority of commercial products use proprietary licenses. Usually each product has it's own specific license. I'm not aware of any reusable proprietary license.

Open licenses

The main goal of open licenses is allowing users to do much more than a typical proprietary license and at the same time preventing absolute exploitation of the author's work. Various open licenses aim to create a win-win situation where users can enjoy larger freedom and the author can keep benefits of the work (not necesserarily money).

When choosing an open license, the primary difference between them is the level of openness:

• High: allowing basically any type of redistribution and derivative work which can greatly increase work popularity and reusability but also significantly limit potential benefits of the author.

• Low: allowing a smaller set of priviledges for the users but keeping a lot of author's rights.

We can say that public domain is the ultimate "maximum open" variant and typical proprietary license is the ultimate "minimum open" variant. Obviously there are lots of licenses in between.

No matter the type of the work, vast majority of open licenses share these elements:

• distribution and modification: the work can be freely distributed and modified

  • some licenses require an attribution of the original work

  • some licenses require to state changes

  • some licenses require source discloure and/or same license for derivative work

• private use: derivative works can violate license requirements as long as the use remains private

• limited liability / no warranty / no trademark - even though not required, most licenses will state explicitly that they grant no warranty and trademark rights

• commerciality: explicit permission or prohibition of commercial use of the work

There are 2 main kinds of open licenses:

• permissive

• copyleft[wiki_copyleft]_[GNU_copyleft]

Both grant a large array of rights but copyleft licenses have 2 additional requirements:

• all derivative work must be under the same license

• all derivative work to be available in the preferred working form (that is source code with no obfuscation)

Advantages of copyleft:

• The work is protected from some forms of reuse which could be generally thought as theft and abuse. Basically same fair play game as with SA variants of CC licenses, which force derivative works to "give back" to the original author.

• If someone creates a copyleft-derivative work and commercializes it, everyone can do it aswell as the license requires source disclosure. In practice this incentivizes people to cooperate instead of agressively copying and selling each other's versions.

Disadvantages of copyleft:

• A lot of potential users (especially programmers and businesses who would like to use the project as a 3rd party library) will be turned off by the license as it effectively forces them to license their entire project under exact same terms.

• It significantly limits license compatibility of such work.

• It's very hard to get large amount of uses of a copyleft project in a place where there are alternatives with permissive licenses.

License domains

Not every license is applicappble to every type of work. We can distinguish 2 primary domains in which majority of open licenses operate:

• software

• creative works (sounds, images, modelling etc.) (not necesserarily in digital or analog form) referred later as art

Some works require more specific licenses:

• Databases - there are various concerns regarding privacy.

• Fonts - modern font formats often combine art with some software. Designing a typeface is definitely an artistic work but because of various technical peculiarities modern fonts also embed a sort of virtual machine code that instructs rendering software how to handle specific details. This makes fonts a combination of both, a situation which some deemed significant enough to design licenses specifically for fonts.

• Hardware - I see more and more projects with the goal of open hardware specification. Hardware is definitely different from software but I don't know exact reasons why they need separate license. Probably dual-use concerns.

Obviously you should choose an appropriate license, made for your type of work. Otherwise, the exact terms and conditions become unclear and you risk various problems caused by dubious interpretation.

What if my work mixes multiple types?

Generally, you can apply multiple licenses and/or divide your work into smaller parts. More further down the article.

Art licenses

We start with licenses for art as their situation is simpler than software and many of readers may be familair with Creative Commons or at least have reused some of the work under one of their licenses (usually work available on Wikipedia or its sister websites).

Creative Commons is a global nonprofit organization that enables sharing and reuse of creativity and knowledge through the provision of free legal tools.[CC]

The organization has created a set of licenses with varying rights and conditions for users. All of the variants are different compositions of their core elements. We will start with the simplest one and move towards more rich variants.

Other CC variants

Based on previous explanations you should easily understand remaining variants:

• CC-BY-NC-SA

• CC-BY-NC-ND

CC summary

An image for easier remembering:

If you are working on some project and are undecided on its license, Creative Commons recommends CC-BY-SA. ND and NC greatly disincentivize users (read: potential investors) while BY and SA are standard elements of free cultural works.

CC Licenses briefly explained: https://creativecommons.org/about/cclicenses/

CC FAQ: https://creativecommons.org/faq

Software licenses

The situation here a bit more complex than with art as software faces many technical peculiarities. The primary organization in play here was FSF but numerous other organizations have created their licenses too, many of which also are in wide use today. A lot of software licenses have analogical elements to CC licenses, they just are better suited towards licensing code.

As previously, we start with most permissive ones but in this case I list only popular ones. The spectrum is much wider here, some licenses aren't a straight increase/decrease in conditions and permissions. There are many more software licenses than mentioned in this article.

Extra licenses

Licenses aimed at specific works that aren't strictly art or software.

Linux kernel

The Linux kernel is very often given as an example of a great open project. Some noteworthy facts:

• The project is licensed under GPL 2.0, without "or any later version" clause and with an explicit syscall exception (Linux-syscall-note) so that programs that rely only on kernel's interface are not considered derivative works. This allows non-GPL code to run on Linux without license violations (GCC has similar explicit exception for the runtime of its toolchain).

  • Linus Torvalds has described licensing Linux under the GPL 2.0 as the "best thing I ever did".[Torvalds_GPLv2]_

  • Linus Torvalds decided not to adopt GPL 3.0 for the project and continues to be against it.[Torvalds_GPLv3]_

  • Linux kernel for a long time has been including binary blobs, which are proprietary, in its source tree and main distribution.

• Even though the primary goal of GPL is FOSS, `not all GNU/Linux distributions are considered free by GNU <https://www.gnu.org/distros/free-distros.html>`_. The views of Richard Stallman (FSF) and Linux Torvalds (Linux) regarding free/open/proprietary software are significantly different.

Applying a license

For software there is a very strong convention: a file named LICENSE or COPYING (extension may vary, usually none or txt) in the root directory of the repository. Additionally, very often all source code files will contain a comment at the top with short license notice. If distributed in the compiled form, it should be bundled with documentation.

For other works, if they use a medium capable of transmitting text or image (especially books and movies), the license (either a note/link or its full form) is provided at the beginning/cover or at the end of the work. Almost any type of creative work has at least a place to put the title and/or author's name so if there is no better place for a license notice this can be used too.

SPDX

The Software Package Data Exchange® is an open standard for communicating software bill of material information, including components, licenses, copyrights, and security references. SPDX reduces redundant work by providing a common format for companies and communities to share important data, thereby streamlining and improving compliance.

The SPDX specification is an international open standard (ISO/IEC 5962:2021).

SPDX is probably best known for it's list of license IDs which are commonly found within comments at the top of files belonging to open projects.

Multiple licenses

There is nothing stopping you from offering the same work under multiple licenses (as long as the work is yours or all contributors agreed to it). Some projects have multiple (usually similar) licenses in order to achieve higher license compatibility with potential derivative works. Some projects are offerred under both open source and proprietary licenses - the goal is to allow users to obtain proprietary license (for a price) if they do not want to satisfy requirements stated in the open one.

Typical combinations are:

• CC0/The Unlicense + dedication to the public domain

• MIT (Expat) + Apache 2.0

• MPL/LGPL/GPL + any later version of these + proprietary

Changing a license

It's possible to change a license. You just need to have an agreement from contributors as they have provided their work under specific terms.

In some projects, there is a contributor agreement required prior to any contributions, some may state that contributors grant patent rights and allow the owner to change the license. If not, the owner must ask contributors for the permission to change the license. See https://en.wikipedia.org/wiki/Software_relicensing for many historical examples.

Be aware that users of the work might react negatively to license change, especially if the new license has more requirements and/or is incompatible with already existing derivative works.

Lastly, law does not apply to the past: all previous versions of the work retain the license they were released with. Even if you change the license, everyone has the right to continue using old versions of the work under terms these versions were released.

License compatibility

It's possible to create a project where multiple subprojects are licensed differently, the final work just has to:

• satisfy all requirements of licensed subprojects

• offer no more rights than licensed subprojects

This means that generally:

• ...the most restrictive license has to be applied to the whole work.

• ...permissive licenses are compatible with each other as all of them allow relicesing derived works, usually with no or simple requirements like attribution.

• ...copyleft licenses are not compatible with each other as almost every one requires the project under exactly the same license.

FAQ

Are there software license equivalents of CC's ND and NC variants?

No. I presume the reasons are:

• NC is just pointless. Sooner or later any worthy software finds commercial application and forbidding this would basically block the development. If you are scared someone could reuse your work for their financial benefit just use one of the strongest copyleft licenses (GPL or AGPL) - if they do you will be able to do the same.

• ND is even more pointless. Code is constantly changed.

If I choose a license that has no NC condition or equivalent (that is, it allows derivative works to be sold) isn't it removing primary benefit of my work? I could create something and someone else could gain all the money for selling my altered work.

Not always. The lack of NC may greatly increase popularity of your work which in turn can led you to obtain numerous benefits including sponsorship or a specific job offer. So it's possible that without non-commercial condition you can actually end up with more money. Whether a given work would be better with or without NC is a question really hard to answer. IMO Jimmy Wales (founder or co-founder of Wikipedia) gives very good answers when asked why the website is free (just search for any interview).

GCC and related libraries (especially libgcc and libstdc++) are licensed under GPL. Does it mean if I use these in my projects all my work has to be licensed under GPL?

GCC and related libraries are licensed under GPL, but the contain Runtime Library Exception. This exception allows to ignore GPL requirements as long as (sic.) all Target Code was generated by Eligible Compilation Processes. Exact details are explained on https://www.gnu.org/licenses/gcc-exception-3.1-faq.html. In the simplest case, if you are using GNU libraries as your runtime (e.g. libstdc++ as the implementation of the C++ standard library) (statically or dynamically) code depending on it is not considered derivative work and GPL does not apply to it.

If my C or C++ code includes Linux system headers, isn't my work derivative given Linux is licensed under GPL 2.0?

Similarly to GCC's Runtime Library Exception Linux has Linux syscall exception which does not consider works derivative if they only use the headers to compile the program.

Can I compile non-GPL code with GCC without license requirements?

Yes. In such case GCC is only a tool used to create the work. It's not a part of the work.

Are FOSS, CC, FSF or other movements/organizations against copyright or capitalism?

Absolutely not. Open licenses are just a different form of copyright, often aimed at making best use of capitalism based on the idea of voluntary trade between parties. Open licenses specify how this "trade" is supposed to happen and given the fact that any "trade" (here: use of the work under specific conditions stated in the license) is voluntary it's a win-win situation for both parties. It's not so rare to see a company which will sponsor a FOSS project and/or ask the maintainers to do some modifications for a price. Other companies develop projects with copyleft licenses and offer private proprietary licenses (Qt is a good example of such project).

Did someone really asked the previous question?

No, but some people greatly misinterpret the meaning of FOSS movement and some people involved in free software movement have even been accused of communism [citation needed]. All such accusations had no solid reasoning and were usually (if not only) from proprietary software companies made in order to stop them from sharing FOSS that was seen as a competition.

FOSS vs open-source

FOSS stands for free and open source software. The word free here does not mean "zero price" but "freedom".[GNU_free] FOSS does not have to be non-commercial.

Open-source is a subset of FOSS. A prime example of a project that is open-source but not free (in FSF terminology) is Visual Studio Code:

• The repository is open and licensed under MIT

• Official Microsoft's releases have specific, different non-open license and contain closed-source telemetry

• The extension marketplace is proprietary to Microsoft and only Microsoft products are allowed to use it

• Several extensions are proprietary to Microsoft, this includes some of Microsoft's official C++, C# and remote development tools

The FOSS version of VS Code is VS Codium - https://vscodium.com/

More information:

• https://www.gitpod.io/blog/open-vsx/

• https://github.com/VSCodium/vscodium/blob/master/DOCS.md

Intellectual property

GNU criticizes this term as it tries to bundle copyright, patenting, trademark and other laws under one term which only causes more confusion and uncertainty.

Cryptography

Various jurisdictions place requirements on cryptographic software. Today's assymetric algorithms are practically unbreakable. Some jurisdictions place hard requirements like intentional backdoors for the government and other jurisdictions consider such actions a violation of their consitutional law (privacy and free speech).

More information: http://www.cryptolaw.org/

License violations

Majority of license violations are for projects under GPL and other copyleft licenses.

• https://www.gnu.org/licenses/gpl-violation.html

• https://gpl-violations.org lists more than 100 cases

Generally, if any lawsuit appears, it can be separated into 2 parts:

• requirement to cease the violation

• recompensation for damages

If a GPL-like license is violated, requiring to release all source code is only the first part - ensuring compliance. The second part is more complex and its finale will generally depend where the lawsuit was filed and what organizations were involved. In some cases the parties finish on a monetary agreement.[wiki_litigation]_

Limitations and exceptions to copyright

Various jurisdictions define different terms that limit copyright or provide some exceptions. These aim to prevent abusive licensing and help general public interest. There is no large international consensus on copyright limitations and exceptions so I list only core elements:

• Idea-expression distinction - ideas can not be copyrighted, only their expression. For example, a book or a movie can be copyrighted but the idea of specific character/story (e.g. femme fatale) can not. This exception also applies to abstract science - it's not possible to copyright mathematical formulas or discovered laws of physics.

• Threshold of originality - the work must be original enough, must contain sufficient effort in order to be copyrightable. How exactly the threshold is defined and whether given work achieves it is very subjective.

• Fair use/dealing - ability to ignore copyright under specific circumstances for the benefit of general public (usually very extreme circumstances like saving lifes in a natural disaster). The simplest case is the right to quote - you don't need to ask the author for permission when your work quotes parts of other's work.

More

Additional resources you might be interested in:

• https://tldrlegal.com/ - software licenses in plain english

• https://www.gnu.org/philosophy/philosophy.html

• https://en.wikipedia.org/wiki/Limitations_and_exceptions_to_copyright

• https://en.wikipedia.org/wiki/Fair_dealing

• https://en.wikipedia.org/wiki/Fair_use

• https://en.wikipedia.org/wiki/Right_to_quote

• https://en.wikipedia.org/wiki/Threshold_of_originality

• https://en.wikipedia.org/wiki/Freedom_of_panorama