How can free licenses such as GNU and CC apply to me when I did not sign them?
<p>In the <a href="https://www.gnu.org/licenses/old-licenses/gpl-2.0.fr.html" rel="nofollow noreferrer">GNU GPL v2</a>, the 5th paragraph is written as :</p>

<blockquote>
  <ol start="5">
  <li>You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or
  distribute the Program or its derivative works. These actions are
  prohibited by law if you do not accept this License. Therefore, by
  modifying or distributing the Program (or any work based on the
  Program), you indicate your acceptance of this License to do so, and
  all its terms and conditions for copying, distributing or modifying
  the Program or works based on it.</li>
  </ol>
</blockquote>

<p>The <a href="https://creativecommons.org/licenses/by/4.0/legalcode" rel="nofollow noreferrer">Creative Commons</a> do nearly the same just before section 1 :</p>

<blockquote>
  <p>By exercising the Licensed Rights (defined below), You accept and
  agree to be bound by the terms and conditions of this Creative Commons
  Attribution 4.0 International Public License ("Public License"). To
  the extent this Public License may be interpreted as a contract, You
  are granted the Licensed Rights in consideration of Your acceptance of
  these terms and conditions, and the Licensor grants You such rights in
  consideration of benefits the Licensor receives from making the
  Licensed Material available under these terms and conditions.</p>
</blockquote>

<p>I am not a lawyer so I don't understand: how can something I didn't signed, or maybe even read, apply to me ?</p>

<p>What if I create a slightly different version of the license, and add "by using my image/tool/software, you silently accept to give away your soul to me" somewhere in the text ?</p>

<p>If you have human-readable documentation of how this work, I'd be very grateful (all stuffs I found on google were way to hard for a muggle like me).</p>

<p>Without a license, you have no right to copy or distribute someone else's work. Suppose you copy or distribute against the terms of the license. Either you didn't agree to the license, and therefore had no right to do as you did; or you did agree and still violated the terms of the license anyway. By the law of the excluded middle (accepted or not accepted), you infringed either way.</p>

<p>It's simple: It doesn't apply to you. </p>

<p>A license gives you permission to do something. If you don't agree to the license, then you don't get the permission. With GPL licensed software, the license gives you permission to make and distribute copies, and to create and distribute derived works, as long as you follow the terms of the license. </p>

<p>You are absolutely free not to agree to the license; if you don't agree then you only have the right to do things that copyright law allows you to do, and making and distributing copies, creating and distributing derived works, are all not things that copyright law allows you to do. </p>

<p>Making and distributing copies, creating and distributing derived works, are all copyright infringement, which means they are illegal, you can get sued for it, you can be forced to pay damages. Worst case go to jail. In the case of the GPL license, doing these things while agreeing to the license, but not following the conditions set in the license, is also copyright infringement. </p>

<p>To amplify on Patrick87's answer, copyright law means you can't take / copy someone else's program. With most software, you do not acquire the software, you acquire a license to use the software – you might have paid for the license, or it might be free. If you managed to actually buy the software itself (because the associated document says "You are buying a single copy of the software itself" – kind of a meaningless statement but you could use that to show that the vendor saw the transaction as being like a book sale), then as the owner of a copy, there are additional things you can do (resell due to 17 USC 109, make a backup copy under 17 USC 117). Since there is no initial transfer of ownership in the typical case of software licensing, the relevance of copyright law is that it establishes the basis for prohibiting you from using the software. So if the US government creates a program, it is not protected by copyright. I haven't digested 17 USC 108 to the point that I say why a library can't marginally override software license conditions, since libraries are granted superior rights compared to ordinary citizens.</p>

<p>The license would be subject to contract law conditions, however. Suppose that there is a clause requiring you to kill yourself after using the software for a year. That clause would not be enforceable, since it is an unconscionable term. If the agreement is held to be void, you won't have to kill yourself, but you may not be able to cannot continue using the software, since the contract could be voided. Courts have the liberty to rewrite contracts, so they could modify the "extended use" term and require you to say "Thank you for the software" (errh, no, that would violate the First Amendment, but they could substitute something else).</p>

<p><strong>this answer refers to English law, but the principles were in place in the days of empire. Around 1/4 of the worlds legal systems have inherited these base principles, but may have made local revisions to some aspects.</strong></p>

<p>Under English law, for a contract to exist, all 4 of these aspects must be in place.</p>

<ul>
<li>an offer.</li>
<li>an acceptance.</li>
<li>an intention to create a legal relationship.</li>
<li>a consideration (usually money).</li>
</ul>

<p>With the Gnu Public Licence, there is a clear offer and a clear intention to create a legal relationship (the software licence).</p>

<p>The consideration is the use and legal entitlement to modify and distribute the software.</p>

<p>Within England and Wales, the courts are entitled to infer that you have demonstrated acceptance simply by using the software - and this may be the case more widely.</p>

<p>In other parts of the world, thanks to international treaties on copyright laws, you are faced with the choice of not using the software, accepting the licence agreement or breaching copyright.</p>

<p>There are legal penalties for copyright infringement, but for a failure to observe the terms of a licence agreement, you are only liable for losses endured by the software owner - so if you found yourself in court, I suspect your lawyer would advise you that you did accept the agreement.</p>

licensing creative-commons