&quot;Joint holders can also enforce copyright, though open source codebases work more like collective copyright.&quot;<p>Joint copyright is basically non-existent in the US. For example, you must intend to create a joint work at the time of creation. You can&#x27;t make it joint later on by signing a document saying it&#x27;s joint with someone.  There are other issues too.<p>This is deliberate, as joint owners each own a 100% enforceable set of rights, and the law doesn&#x27;t really want tons of people running around claiming to own the same work.<p>&quot;That said, non-exclusive Linux kernel copyright holders have performed enforcement activities (quietly or noisily)...&quot;<p>Not in the US. It&#x27;s not possible in the US. It&#x27;ll get dismissed immediately.