The Software Freedom Conservancy on GPLv2 irrevocability

For anybody who has been concerned by the talk from a few outsiders aboutrevoking GPL licensing, thisnew section in the Software Freedom Conservancy's copyleft guide isworth a read.

Thus, anyone downstream of the contributor (which is anyone using thecontributor's code), has an irrevocable license from the contributor. Acontributor may claim to revoke their grant, and subsequently sue forcopyright infringement, but a court would likely find the revocation wasineffective and the downstream user had a valid license defense to a claimof infringement.

Nevertheless, for purposes of argument, we will assume that for some reasonthe GPLv2 is not enforceable against the contributor, or that theirrevocable license can be revoked. In that case, the application ofpromissory estoppel will likely mean that the contributor still cannotenforce their copyright against downstream users.