Websites using GPL-licensed libraries
<p>If a customer of yours pays you to develop a website (not to buy it, so he doesn't receive a copy of the software), the website uses GPL libraries or frameworks, and the site is installed in a server of yours, but it has been done "for the use of your customer", are you somehow forced to deliver a copy of the source code to the customer?</p>

<p>In my case, my website uses a GPL-licensed framework (without the linking exception), which is dynamically linked to the executable that runs the site. The code done by me is not licensed (because it's private, I'm the only one that has a copy of the software and runs it).</p>

<p>At which extent is the app being "used" or even "owned" for your customer in particular if he doesn't have a copy?</p>

<p>The GPL licenses were invented precisely to protect the rights of the user of the software, but was mainly meant for protecting the rights of the user that owns and runs a copy of the software, so they can inspect what is the software doing in his computer and also change its behaviour, because a software makes a user dependent on it.</p>

<p>However, a website is used for everybody with access to the Internet, is not something that users "run", and your customer is a special mention among all of these users, because him is who dictates how must that sofware behave, but has no direct control over it.</p>

<p>Under the GPL, if the software is not distributed to the user then it there is no need to make the source code available. It is only necessary to make source code available for GPL licensed software that is modified and distributed.</p>

<p>From the <a href="https://www.gnu.org/licenses/gpl-faq.en.html#UnreleasedMods" rel="nofollow noreferrer">GPL FAQ</a>:</p>

<blockquote>
  <p><strong>A company is running a modified version of a GPLed program on a web
  site. Does the GPL say they must release their modified sources?</strong></p>
  
  <p>The GPL permits anyone to make a modified version and use it without
  ever distributing it to others. What this company is doing is a
  special case of that. Therefore, the company does not have to release
  the modified sources. The situation is different when the modified
  program is licensed under the terms of the <a href="https://www.gnu.org/licenses/gpl-faq.en.html#UnreleasedModsAGPL" rel="nofollow noreferrer">GNU Affero GPL</a>.</p>
  
  <p>Compare this to a situation where the web site contains or links to
  separate GPLed programs that are distributed to the user when they
  visit the web site (often written in JavaScript, but other languages
  are used as well). In this situation the source code for the programs
  being distributed must be released to the user under the terms of the
  GPL.</p>
</blockquote>

<p>As long as you are not using software licensed under the <a href="https://www.gnu.org/licenses/agpl.html" rel="nofollow noreferrer">GNU Affero GPL</a> then there is no need to make source code available for software that is only accessed over the network; i.e. it is not downloaded to the user's computer.</p>

<p>As the FAQ states, if you download software to the computer that contains GPL code then you must make that source code available; i.e. JavaScript code that contains elements of GPL licensed code.</p>

software licensing gpl