How to enforce GPL if the copyright holder doesn&#39;t have access to the source code of violating software?
<p>I'd like to publish a C library project that I have written on GitHub and license it under GPL, so I am doing some research on open source licenses and some confusion comes to mind.</p>

<p>Let's say Evil Corps uses and modifies my code in a commercial software without disclosing their source. I have come across their software, and realized that one feature it has is very similar to what my library does. Upon my inquiry, they deny that they have used my code but also refuse to show me their source.</p>

<p>How would I have to proceed in order to enforce the GPL? How is it done in the past to prove that the GPL is violated?</p>

<p>If an infringement suit is filed, the plaintiff(s) would have rights of discovery. They could subpoena the source code in such a case for comparison. They could take the depositions of EvilCorp's developers and ask them about the libraries that they used.</p>

<p>There might well be other ways to achieve the same effect.</p>

copyright licensing open-source-software gpl enforcing-judgment