Is the non-applicability of copyright to software interfaces considered settled law?
<p>In computer software, it's common for a system to expose an Application Programming Interface (API) for other software to interact with it. For example, a smart lightbulb might expose a <code>SetBrightness(value)</code> interface that other software can use to actuate the bulb's functions. Now that the 12-year battle of <a href="https://en.wikipedia.org/wiki/Google_LLC_v._Oracle_America,_Inc.#Decision" rel="nofollow noreferrer">Google v. Oracle</a> is over, with SCOTUS ruling in favor of Google, is the non-copyrightability of software APIs considered settled law?</p>
<p>I was considering using a GPL-licensed library that claims that merely <em>referencing</em> the library's API, even if the library is not actually included in the product, would require the entire project to be GPL. In light of Google v. Oracle, it <em>seems</em> like that claim is no longer valid. Is my interpretation correct, or am I missing something? Obviously, anyone can sue anyone for anything, but in light of the SCOTUS decision it seems that if the author of a GPL library were to bring suit against another for using the API <em>without the library</em>, it would probably be easy to get a summary dismissal with that case as the basis.</p>

<p>This is not settled law: neither the copyright question, nor the fair use question.</p>
<p>In <a href="https://supreme.justia.com/cases/federal/us/593/18-956/#tab-opinion-4382274" rel="nofollow noreferrer"><em>Google LLC v. Oracle America, Inc.</em></a>, 593 U.S. ___ (2021), the US Supreme Court addressed the reproduction of a <a href="https://law.stackexchange.com/a/9530/46948">subset of the Java API</a>.</p>
<p>The majority assumed for the sake of argument that the Java API was protected by copyright, but went on to hold that the reproduction was a fair use.</p>
<blockquote>
<p>We shall assume, but purely for argument’s sake, that the entire Sun Java API falls within the definition of that which can be copyrighted. We shall ask instead whether Google’s use of part of that API was a “fair use.” Unlike the Federal Circuit, we conclude that it was.</p>
</blockquote>
<p>So, it is an open question whether an API is protected by copyright, but the precedent from the Federal Circuit will be persuasive authority. The Federal Circuit held that the API is protected by copyright and the Supreme Court did not upset that conclusion.</p>
<p>Second, the factors that led the court to conclude the reproduction of part of the Java API was fair use could turn out another way in another fact scenario. Some of the reasoning seems to generalize, but some seems specific to the Java development ecosystem. Briefly, the court recognized:</p>
<ul>
<li>API authorship is a creative process, but is &quot;functional in nature&quot;</li>
<li>The reproduction was intended to assist interoperability; it was commercial; there was no evidence of bad faith</li>
<li>The amount of code taken was a small amount of the entire Java work, an amount consistent with its goals</li>
<li>The market harms to Oracle were dubious</li>
</ul>
<p>My prediction is that there will continue to be significant case-by-case uncertainty as to the applicability of the fair-use defence in this context.</p>
<hr />
<p>However, <em>Google v. Oracle</em> was about API <em>reproduction</em>, not API use. It said nothing about a claim &quot;that merely referencing the library's API, even if the library is not actually included in the product, would require the entire project to be GPL.&quot; The question in your second paragraph is best asked as a separate question.</p>

united-states copyright software open-source-software case-law