From Wikipedia, it states that EULA is different from OSSL

Unlike EULAs, free software licenses do not work as contractual extensions to existing legislation. No agreement between parties is ever held, because a copyright license is simply a declaration of permissions on something that otherwise would be disallowed by default under copyright law.

I am a bit confused about the Open Source Software License (OSSL) and EULA. In my understanding, Open Source Software License seems to be covering a wide area of aspects, including both users and developers, as mentioned in the MIT license:

...without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, ...

while EULA seems to be applying only to the end-user who is going to use the software. So the idea of EULA is more or less already included in Open Source License. Am I right?

For a project that is licensed under MIT license (or possibly other Open Source Software Licenses), Do I still need to provide an End-user License Agreement when distributing the software to protect myself? Is there any contradiction between them? Or asking the user to understand and agree to the MIT license before installation would be sufficient to avoid any liability issues?


Free software and open source licenses

Free software and open source licenses seek to grant additional rights, beyond those granted by copyright law. Strictly speaking, such licenses cover the acts of distributing and modifying software, not directly the act of using it. Copyright law controls who can distribute and modify software; if you obtain software from a legal distributor, you may use it even if you don't accept the license under which it is distributed. This is made explicit in the GPL, section 9:

  1. Acceptance Not Required for Having Copies.

    You are not required to accept this License in order to receive or run a copy of the Program. Ancillary propagation of a covered work occurring solely as a consequence of using peer-to-peer transmission to receive a copy likewise does not require acceptance. However, nothing other than this License grants you permission to propagate or modify any covered work. These actions infringe copyright if you do not accept this License. Therefore, by modifying or propagating a covered work, you indicate your acceptance of this License to do so.

Note the trigger: you accept the license by modifying or propagating the software, not by using it.

Some licenses, such as the MIT license you quote, explicitly grant the right to use software, but this isn't necessary — you already have that right, assuming you obtained the software legally. The free software definition itself didn't mention it initially, but it was later added as freedom 0; having it explicitly mentioned in the definition helps clarify that licenses may not limit the uses of software.

Free software licenses also protect the developers by limiting the provided warranty; e.g. in the MIT license:


End-user license agreements

End-user license agreements generally seek to remove rights granted by copyright law, and to re-define the ownership of software. They are triggered at the latest by running the software, but more typically they are triggered during installation or even by the act of opening the physical container containing the installation media (this was common for software on floppy disks; the disks were shipped in envelopes, and tearing the envelopes open was taken as signifying acceptance of the EULA). There is some debate as to the validity of click-through licenses (or tear-open licenses), but that's beyond the scope of this answer.

One common feature of EULAs is to state that software is licensed, not owned, so the user doesn't own a copy of the software but only a license to use it. (This removes the rights granted by copyright law to legitimate owners of an artifact.) They also generally forbid modification and distribution.

Hopefully this clarifies the differences. You don't need a EULA to protect yourself as a developer; if you're particularly worried about some types of protection, you can look at the different open source licenses in existence and see the kinds of protection they grant, in particular with regards to patents. In fact, if you do try to enforce a EULA, you'll find that most (if not all) authorities in the matter would consider your software to be non-free (not open source), regardless of the license under which it is distributed: your EULA is only enforceable if you deny the right to remove it, which means restricting the types of modifications that can be made to your software...

  • Very detail explanation. However, I want to understand more about the protection to developer given by Free Software License. As you mentioned you(user) may use it even if you don't accept the license under which it is distributed.. If a user has damage when using the software, can he/she claims that he/she actually does not accept the MIT license/GPL and ask for developer's liability for the damage caused? – Calvin Lau May 14 '16 at 16:30
  • @user3259983 that's a good question. The warranty disclaimer is a statement of fact: "the software is provided ...". It is typically repeated in source code alongside the license grant (e.g. in the header documented in the GPL), which serves to re-inforce that. Warranty disclaimers are standard practice in software development, and it would cause quite a furore if they became ineffective (although some people would like that!). I think there is legal precedent for limiting damages to the amounts paid by the user even with a warranty (typically 0 for open source software)... IANAL of course. – Stephen Kitt May 14 '16 at 16:45
  • That makes sense. On the other hand, I notice in most EULA and GPL, they have a line like ...SOME STATES DO NOT ALLOW THE EXCLUSION OF INCIDENTAL OR CONSEQUENTIAL DAMAGES... and in GPL TO THE EXTENT PERMITTED BY APPLICABLE LAW, IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW. What are those states refer to? And does they exert any potential liability issue to developer as well? Thank you. – Calvin Lau May 15 '16 at 3:43
  • I don't know which states are concerned, but that boils down to the fact that legal agreements can't subvert the law — so in those states, nothing will protect you. To get a definitive answer you should probably consult an attorney, to see what kinds of insurance (if any) may be appropriate. – Stephen Kitt May 22 '16 at 12:25

An EULA and what you're referring to as an Open Source Software License (which I'm going to call OSSL, for disambiguation) are the same type of legal document. They're both a license agreement, which grant certain rights to various parties.

EULA's are (generally) used more on proprietary software. They're usually custom-written by the company's lawyers and tailored to the purpose of the software and the rights the company wants to grant. They're generally more focused on protecting the company from unauthorised use of its software.

OSSL's are usually more general documents. They're written once (or a few times - looking at you, GPL), and are intended to be applied to many different types of software. The only thing the different software projects have in common is that they're open source. OSSL's are more focused on protecting the consumer from the author suing for copyright infringement, and they explicitly grant rights to this end.

You only need to - and only should - apply one of these documents to your software. If you want to have a permissive open source project, a license such as the MIT license would suit. This grants consumers the right to use, modify, and re-distribute your work as long as your copyright notices are kept intact.

  • I am not sure if EULA is the same kind of document with OSSM because from Wikipedia, it mentions Unlike EULAs, free software licenses do not work as contractual extensions to existing legislation. – Calvin Lau May 14 '16 at 10:27
  • @user3259983 There are minor differences like that, yes. However, both are the same broad type of document - a license agreement, which grants rights to the end user. – ArtOfCode May 14 '16 at 10:51

In most legislations, software is copyrighted with the act of creation. The initial copyright holder is/are the developer(s), who may either transfer it or waive it altogether, placing it in the public domain (though the latter may not be possible in some legislations).

Unless the copyright holders have waived their copyright, any copying, modification or usage requires a license from the copyright holder, and the terms of the license determine the rights and obligations of both parties. This goes for both proprietary and FOSS software – what differs is the name given to the license agreement and the rights of its parties.

EULA is the term commonly used in connection with proprietary software. It is a "contractual extension to existing legislation" in that it is the kind of licensing agreement lawmakers originally had in mind: the licensee may use the copyrighted work subject to the terms and conditions of the agreement, and the copyright holder explicitly reserves all other rights. With commercial software licenses, the licensee typically receives a right to receive the software, but not to redistribute, modify or reverse-engineer it. Beyond that, most EULAs limit the liability of the copyright holder for any damage arising from the licensee's use of the product.

Agreements allowing viewing code, modification, redistribution etc. of proprietary sources do exist (typically between companies), but these are typically separate from the general EULA.

FOSS licenses work in a different way. Open-source licenses explicitly grant the licensee the right to use, redistribute, examine the source code of, and modify the software, thus effectively eliminating the "all (other) rights reserved" part and covering not only the scope of the EULA but also that of the specialized licenses mentioned before.

Free (or "copyleft") software licenses have two additional requirements over open-source licenses: distribution of executable binaries is only allowed under the condition that source code is also provided, and any modified versions of the software must be placed under the same license (some exceptions may apply, such as allowing other licenses of a similar spirit).

Both are more than just "contractual extensions to existing legislation": with an open-source license, the developers waive most (or all) of their exclusive rights. Free software licenses additionally use copyright as a vehicle to prevent works derived from the original software from being placed under a commercial license – neither of these was originally intended by the creators of copyright law, but these constructs are nonetheless possible and have since been tested in court.

Like an EULA, both free and open-source licenses frequently exclude liability. Unless the license states that certain uses (such as mere usage of the software) do not require acceptance of its terms, they effectively replace the EULA in governing the legal relationship between the copyright holder and the end user.

Aside from copyright, product liability issues need to be considered. Details depend on legislation, but eventually a FOSS developer cannot rule out being someday be held liable in some part of the world for their software malfunctioning. Therefore, the license would either need to include a liability exclusion that applies to end users even if they do not intend to modify or redistribute the software, or the developer would need to add an extra agreement which excludes liability to end users (note, though, that adding an extra agreement may not be compatible with the requirement of free software licenses to redistribute the software under the same license).

Disclaimer: I am not a lawyer.

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