body: Recently, a `node` software developer asked that his packages be un-published from an index of software packages called "npm" when the developer was threatened with trademark infringement. The package un-publication caused a cascade of functionality problems with software dependent on one of these packages.
  
  
  The developer had not explicitly revoked their license, this question is related but on a more general focus. What if the core open-source packages we depend on so critically were suddenly revoked and re-published with different terms, or none at all? Can we create a derivative work based on previously published terms? If we've already created a derivative work bound by the same license as the original author, are we infringing if they revoke the original license?
  
  
  The specific [wording of the most popular licenses](https://opensource.org/licenses) do not explicitly grant for any particular term. Does that mean it's only valid until explicitly revoked, or perhaps it's valid perpetually/until copyright expires?
  
  
  Possibly relevant cases:
  
  
  * TV Globo v. Brazil Up-Date Weekly
  * Rano v. Sipa Press
  * Walthal v. Rusk
  
  
  
title: Duration of a license granted without specific bound