Can i legally claim to own a derivative Open Source project?
<p>The Apache license states the following:</p>

<blockquote>
  <p>You must cause any modified files to carry prominent notices
            stating that You changed the files.</p>
</blockquote>

<p>However if i rewrote the original source can i claim it as my own and therefore relicense it?</p>

<p>If you are the sole copyright holder of the software – in particular, if the software does not contain parts that were authored by other people – then the existing license has no direct effect for you. As the sole copyright holder you would be able to license it however you want (<em>re</em>-licensing probably isn't the best term here).</p>

<p>But: are you sure that you are the sole copyright holder, and that your modified version is not a derivative work of the original in the sense of copyright law? It's not possible to answer that in a general way, as derivativeness is ultimately for a court to decide. I think you would have to completely rewrite every file of the project from scratch to effectively remove other people's code.</p>

<p>Any edits you make do give you a copyright to your edits (assuming they rise to the level of copyrightability). So you do get a small <em>part</em> of ownership of the software. There are two things to keep in mind though:</p>

<ol>
<li>You have no right to edit the software except through the license. By making changes you agree to the license.</li>
<li>Having a small part of the copyright in the software is practically useless, and does not allow you to claim total ownership.</li>
</ol>

<p>Since the Apache license is a permissive open source license, software under this license can generally be used without having to relicense it. The license gives you very broad rights to the software, with only few conditions. The license's attribution requirements are generally manageable, although the patent clauses can be more problematic. Ask yourself whether the effort of going through a complete rewrite would really be worth it for complete copyright ownership of the software.</p>

open-source-software