I previously released a work under GPL, can I release the same work under another license?

Question

Some time ago, I wrote a small program to automate a simple task. At the time, I released the program under the GPL license. I'm the sole author of the work and it was not created for hire (I was not under employment contract while making it or being paid for it).

Now I've been contacted by someone who has reused and incorporated the work, who at the time did not notice it was licensed under GPL. I've been asked if I'd be willing to release the work under another license so they can keep using my work as part of a closed source commercial project. (Something they wrote at work).

I'm not against this, but am I even allowed to do that? Am I free to rescind the share-alike requirement of GPL by just issuing the same work under another, more permissible license?

Can I say "I release this to you under $license additionally?" I was thinking cc0 to completely wash my hands of it, but is that even possible? I don't want to expose myself to any liability doing this.

Answer 1

Yes, you can license the work under new terms to everyone or just to this one person, as you like.

You don't need to release a new version to add a license. If you did, then companies that sell licenses to use their software would have to bump the version number every time somebody bought one.

Am I free to rescind the share-alike requirement of GPL by just issuing the same work under another, more permissible license?

You aren't rescinding anything. The person you're granting the new license to never accepted the terms of the GPL. The GPL has no power over them. The only reason anyone chooses to follow the requirements of the GPL is that it grants them some rights if they do. Using the software doesn't automatically make them subject to the GPL, it just makes them guilty of copyright infringement if they don't abide by the GPL and their use isn't covered by some other license or by fair use, etc.

This person did infringe on your copyright. As the sole copyright owner you can handle that by simply choosing not to sue them. If you want to bind yourself legally to never suing them, then... why are you being so nice? It's their fault they infringed, if I were you I'd ask for some money. But if you want to tie your own hands for whatever reason, then I'm not sure how you'd do it. You should ask at the Law SE, or see if there's an existing question there that covers it. A new license can prevent future infringement, but I don't think you can make it retroactive such that the earlier infringement never happened. I may be wrong.

Answer 2

In general, as you are the sole author, you can release your work under any license and you can change the license at your will.

Since you cannot change the licence retroactively, you cannot say "Version x.y.z which was under GPL from today is under your-needed-license".

So I think that the the simplest solution is for you to relase a x.y.z+1 version under another license (or a dual lincese if you wish) and as long as they use that new version, they are in the clear legally even in the future or against some third part that can challenge them about licensing issue. (being a closed source commercial product, you can not care if they use it, but some of their competitor can try to provoke some legal issues to them, even if I don't see how)