It's been a while since I read the GPL3, so I just read it again. I'm no lawyer, but if I'm understanding correctly, yes, it does have to be licensed under the

It's been a while since I read the GPL3, so I just read it again. I'm no lawyer, but if I'm understanding correctly, yes, it does have to be licensed under the GPL3, but it doesn't have to be licensed only under the GPL3. With a license like MIT, the could apply a second license which would, for example, amend the MIT license to require you to pay for the software. However, the "No Further Restrictions" paragraph in the GPL I think puts a much stronger set of requirements: > You may not impose any further restrictions on the exercise of the rights granted or affirmed under this License. For example, you may not impose a license fee, royalty, or other charge for exercise of rights granted under this License, and you may not initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging that any patent claim is infringed by making, using, selling, offering for sale, or importing the Program or any portion of it. This is why I think Stallman often uses the language "licensed with terms at least as open as the GPL" instead of saying "licensed under the GPL"--yes, it has to be licensed under the GPL3 but that doesn't quite capture the whole story. Someone can apply another license (i.e. Apache 2, to explicitly grant patents) so their licensing might not be just the GPL3, but further licenses can only expand freedoms, not restrict them. I would encourage anyone who is interested in this sort of thing to read the license for themselves. Don't get intimidated and assume it's all in legalese: while I'm hesitant to think I understand it since the law is not my area of expertise, the GPL is written in what seems like fairly straightforward English.