software open-source-software gpl
Do I have to adhere to my own software licences for them to remain enforceable?
<p>I have written a software application and an accompanying software library. When users use this application, they will write code externally to it which also makes use of the software library. The application will then use the code that they have written.</p>
<p><a href="https://i.stack.imgur.com/ByHxE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ByHxE.png" alt="Diagram" /></a></p>
<p>I have chosen to licence the library under the GNU GPL 3.0 licence. Please correct me if I am wrong, but my understanding is that the GPL 3.0 requires all derivative software to also be licenced under the GPL 3.0. This was a large reason for why I chose it. By releasing the library under GPL 3.0, so must all of the code written by users which makes use of it. This also means that my software application itself must be licenced under the GPL 3.0.</p>
<p>Am I able to break the rules of the GPL 3.0 and close-source/copyright the application while still having the library be GPL 3.0? If I do break the licence, can the licence remain enforceable for the software written by others?</p>

<h2>You don’t need a licence to use your own IP</h2>
<p>It’s yours, do what you like with it.</p>
<p>If you choose to licence your IP to particular people or the world at large they must follow the licence(s) you grant irrespective of what you or anyone else does.</p>

<p>A license is a <em>permission</em> to let someone else use your software which would otherwise be subject to copyright (assuming you have correctly asserted copyright right by placing a valid copyright notice in a prominent place, e.g. &quot;© Copyright 2018 Toby Smith, all rights reserved.&quot;). For the copyright be enforceable (i.e. a claim filed in court) in the US, it needs to be registered with the Library of Congress for a fee, though that can be done later.</p>
<p>However that permission does not put any constraints on what you want to do with the property.  Perhaps you want to license it to someone else under a different license? Sure.  The people using your software under license are obliged to follow the license or face a potential lawsuit for copyright infringement.  You yourself are not bound by the license in the same way as the user, you are bond only in that you are promising not to sue the user of the software for copyright infringement if they use it in accordance with the terms of the license.</p>
<p>You may create derivative works and they would not be subject to GPL <em>except</em> if your original application is a derivative of someone else's GPL'd work, or you are using the modules created by your users, which could also be subject to GPL.  To avoid any possible conflict of you breaking <em>their</em> license to you for use of their software, it might be prudent to obtain a separate (non GPL) license to use their modules.</p>
