Where to put license for MIT licensed code on website

Question

I'm a freelance web developer building a site for a client. I found some code I'd like to use on CodePen which uses the MIT License. As far as I understand the license, I can use the code freely on my client's project so long as I reproduce the MIT License with it.

The code I'm using is comprised of a combination of HTML, CSS, and JavaScript code, which would all reside in different files. How do I include the license in this case?

I see three ways, which I'll list in order of my preference:

1. Comment out the license before each section of relevant code in their respective files. The drawback of this is it isn't obviously visible to the public, so I'm not sure if that is enough. You would need to look at the source code to see it, which not many people do unless you're a developer. This would be most desirable for client as it would be "behind the scenes" so to speak.
2. Create an acknowledgements page with the license referring to the specific code
3. Write the license on the page in which the code appears.

Which, if any of these, is the most appropriate location?

Answer 1

I'm surprised this question doesn't come up more often. It's a tricky issue, and one that is highly open to interpretation.

Disclaimer: I am not a lawyer.

There is not a lot of specific guidance on this issue, but a well-researched overview of the topic was published by The International Free and Open Source Software Law Review, titled "Open source licensing notices in Web applications."

On that page, the author (Arnoud Engelfriet) discusses different means of satisfying license clauses for open source licenses, and some consequences if it's not done correctly. With respect to the MIT license and its requirement to be displayed, Engelfriet has this to say:

This requirement makes it hard to comply without actually including the verbatim text of the license in the Javascript file. We could follow the same approach as with the BSD license and interpret “shall be included” as “must not be removed” but the use of the active verb ‘shall’ makes this a harder interpretation.

The author draws this conclusion:

There is a very real desire to not include full open source license texts in Javascript files when those are downloaded by browsers. For distributions of Javascript projects in original form (with source code, documentation etcetera) this issue is less apparent, as the overhead of a single license file is small.

Virtually all projects that use open source and Javascript in practice simply refer to the license text as hosted on their own website. I found no project that actually copied an open source license text in a Javascript file.

Most open source licenses do not provide obstacles against this practice. As long as the license is identified and available by URL, one may consider this as adequate notice. I therefore conclude that authors of Javascript files can license by including a reference to the license and a URL where the license text can be found.

He ends the article by providing sample text for a possible short form and long form attribution notice, to be included in the file header.

Based on this article and on other Stack Exchange questions about the same subject, I would say (in my non-lawyerly opinion) that if you can reasonably accommodate it, the first option you listed in your question is the best one. However, if you went with option #2, you would probably be fine, as it seems others have taken that same route.

Answer 2

If you're licensing source code, it would make sense to code the license into the source, which anyone can view with a simple browser command, right? You would also be well advised to reference (if not also reproduce) the license in displayed text, perhaps referencing the details to be found in the source of that page, or wherever you have encoded it, if not also a link to its source (as required in CC-BY licenses).