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This article is written by Siddhi Shah who is pursuing a Diploma in Intellectual Property, Media and Entertainment Laws from LawSikho.


When you get a license for your software, it is essentially an agreement between you (or your company) and the user of your software. A software license agreement allows users to use your software and notes down the details as to how they can use it. A Software License Agreement lets the user know how much he is permitted to use the software and what restrictions are imposed on him when it comes to opening, modifying, and redistributing the software. But there are so many licenses out there. How do you determine which license is right for your software? What kind of protection do different licenses offer? How do different licenses restrict a user? Which license is better for commercial purposes and to what extent? Software licenses fall under two main categories based on their restrictiveness: 

  • Proprietary software licenses: 

Proprietary software is a restrictive software license that restricts the user to copy, modify or redistribute in any way. It is the most restrictive license that is out there and is generally used for commercial purposes.

  • Open-source software licenses:

Open Source Software licenses are those licenses where the owner or the creator of the software has copyright over his work but chooses to ease down some restrictions on his work with respect to the opening, modifying, or redistributing the software. Based on the degree of restrictiveness there are two main types of open source software licenses:

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  • Permissive license 
  • Copyleft license

What is copyleft? 

When a person gets copyright of the software, his main intention is to prevent other people from distributing the software. Copyleft is exactly the opposite of copyright. When a person gets a copyleft, he is imposing on the user who modifies anything in the original software that they must keep their version of the software open-source so that it is publically available. Based on the viral effect of a copyleft, there are two categories of copyleft licenses:

  • Weak Copyleft: These are free software licenses that make it compulsory that source code that descended from software licensed under it, will remain under the same, weak copyleft, license. However, it should be noted that it is possible to still link to weak copyleft code from code under a different license (which can also be a proprietary license), or otherwise incorporate it in a larger software. In simple terms, a weak copyleft license applies only to the original copyleft work.
  • Strong Copyleft: These licenses go a step further from weak ones and make it mandatory that any software that links or otherwise incorporates its code would be licensed under compatible licenses, which are a subset of the various available open-source licenses. Because of this, these licenses have been called “viral”. In simple terms, a strong copyleft license applies to all its derived works and the software components in the package.

A GPL, i.e., General Public License, is the most popular copyleft license out there. This license is based on four freedoms: 

  • the freedom to use the source code for any purpose, 
  • the freedom to make modifications, 
  • the freedom to share the source code with anyone, and 
  • the freedom to share changes.

However, it should be noted that GPL does not restrict users from selling derivative works that are based on the original source code; it merely requires source code to be freely available to anyone who wants it.

What is permissive?

A permissive license is an open-source license that guarantees the freedom to use, modify, and redistribute, while also permitting proprietary derivative works. In other words, when a user modifies a software, he or she is not obligated to make their altered software open-source, however, the user usually needs to give credit to the original project.  

MIT licenses are the most popular and commonly used permissive software licenses. This license gives users of software permission to reuse the source code for any purpose, sometimes even if their code is part of proprietary software. As long as users include the original copy of the MIT license in their distribution, they have the freedom to make any changes or modifications to the code to suit their own needs and they can also use it for commercial purposes. In the case of permissive licenses, the owner of the original source code is not liable for any claims or liabilities. Other popular permissive licenses include Apache license, Berkeley Source Distribution License, and unlicensed

Copyleft v. permissive

Both copyleft and permissive licenses allow users to copy, modify, and redistribute code freely. However, the main difference between the two lies in the degree of restrictiveness regarding their distribution. 

When one modifies a copyleft software, one is obligated to keep their new altered code under open source so it can be publically available. Whereas, when one modifies a permissive software, there is no such restriction except to give credit to the original work. The user has the freedom to use the altered code however one wishes to, one also has the freedom to make it proprietary software. 

A derivative work from permissive software can be used as copyleft but a derivative work from copyleft cannot be used as permissive. It should also be noted that in cases where there are any bugs found in the software, the creator would be held liable only if it is a copyleft license and not in a permissive license.

Due to the option of turning an open-source software into proprietary software, Permissive software is usually preferred by companies over a copyleft software they can exploit for their commercial purposes without having to disclose their altered code. 

The main idea behind a copyleft license is that if a user is using any free content, then anything that is made out of it should be free as well. Whereas the permissive licenses do not treat this kind of free-riding as anything harmful, instead, their view on this matter is to seek maximum utility of software by refusing to restrict free-riders from appropriating its benefits. Copyleft content because of the same reason is more likely to go viral than permissive software. Since derivative works under a permissive license are published under different licenses, it is neither persistent nor does it have a viral effect.

Which license is better?

The recent trends show that over the years software developers have been preferring permissive licenses over copyleft. There are many reasons to choose for a permissive license over copyleft:

  • To maximize the use of software and to invite contribution from people and corporations that would otherwise not contribute if it were copyleft: 

From the perspective of companies who are looking for ways to exploit a code commercially, they usually prefer a permissive license over copyleft since, under the permissive license they would be able to turn their derivative work into a proprietary work and use it for commercial purposes, their only obligation under permissive license would be to give credit to the original work.

  • To protect a software package that has very little code:

The Free Software Foundation (FSF) recommends using a permissive license for software less than 300 lines unless the code is especially important. As per FSF, a small code is unlikely to attract downstream developers when the template’s copyleft terms would apply to the whole rendered website.

  • If the real aim is to use the software as a component of a broader service and not to earn profits:

Since software developers don’t always prefer to keep their altered code an open-source, permissive software, therefore, promotes a broader service. Personally, I feel it is better to use permissive licenses over copyleft licenses, as it promotes more modifications and development of the original software since the users have more freedom to use their derivative code in whatever manner they wish to use it.


When software is protected under an open-source license, it means that the creator of the software is opting to ease down the restrictions that would have been imposed on the end-user otherwise. An open-source software essentially includes two main categories of licenses based on their degree of restrictiveness, these are copyleft licenses and permissive licenses. Both copyleft and permissive licenses allow users to copy, modify, and redistribute code freely. However, in a copyleft license, the end-user is obligated to publish his derivative code as open-source and make it publically available. There are two types of copyleft licenses: a strong copyleft and a weak copyleft. Whereas in a Permissive license, there is more freedom given to the end-user, i.e., it is upon the end-user to decide whether he wants his derivative code to be open-source or proprietary, his only obligation is to give credit to the original source code. GPL Licenses are the most popular copyleft licenses available out there, whereas MIT license is the most widely used permissive license. Since a permissive license offers more freedom to the software developers, it is more widely used compared to copyleft. And because of the same reason, it can be more useful for commercial purposes, most companies also prefer it in order to keep their derivative code private.


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