On Tue, 26 Sep 2006 14:14:24 -0400, glyph@divmod.com wrote: I've got what I believe is the final word on this. Phil Thompson (again, Riverbank) says:

""" The reactor must be licensed under the GPL, but the rest of Twisted doesn't. A Twisted application that doesn't use the reactor can be licensed under the Twisted license. A Twisted application that uses the reactor must be licensed under the GPL. """

The best course of action, then, would be to distribute qtreactor separately, since we can no longer say that Twisted is all MIT licensed if we do not. The practical ramifications of this are not earth-shattering, so I think that we do not need to, e.g. release a 2.4.1 which does not include qtreactor, but 2.5+ should definitely not include it.

I also asked specifically about not interfering with the PyQt/Qt commercial license, and Mr. Thompson suggested wording like this:

""" This code is licensed under either the Twisted license or the GPL depending on the license of the copy of PyQt being used.

If the GPL version of PyQt is being used then this code is also licensed under the GPL. Given the viral nature of the GPL this means that any application must also be licensed under the GPL.

If any other version of PyQt is being used (eg. commercial, evaluation, educational) then this code is licensed under the Twisted license. """

I suggest that we leave that wording mostly unchanged.

I agree and think (see disclaimer below) that this is just fine. It does not seem to inhibit the developer's flexibility at all. If you are developing with GPL PyQt, it looks like you can use freely qtreactor, under the condition that distributions of your application (including the copy of qtreactor that it incorporates) are made under the terms of the GPL. Nothing in the licensing of qtreactor could remove that requirement. If you are developing with commercial PyQt, Mr. Thomson's suggested wording indicates that your commercial application can also use qtreactor without any adverse impact on the proprietary nature of your work. This allows people to develop Twisted-based PyQt applications as free software (GPL) or commercially with the purchase of a commercial PyQt license, which is the desirable outcome for both Riverbank Computing and Twisted fans alike. I would think that Mr. Thompson's authorization from TrollTech to dual-license PyQt gives him the ability to authorize this sensible arrangement regarding qtreactor's use of PyQt. It would be nice to have confirmation of that from him as well, however, since anything importing PyQt ultimately has a dependency on Qt itself. If you need someone to host qtreactor, I'd be willing to do so from http://foss.eepatents.com, as long as I had direct assurance from Mr. Thompson that all these questions are settled. I could also contribute a few Twisted-friendly enhancements like the deferred-returning modal dialog box I posted a while back. However, such enhancements will have been developed with the GPL version of PyQt and would not be subject to the special provisions above unless Mr. Thompson chose to offer that as well. Best regards, Ed DISCLAIMER: Nothing in this comment is to be construed as legal advice. Although I probably think about things legal more often than the average person, being a registered patent agent, I am not a lawyer qualified to practice copyright law or anything else outside the representation of patent applicants before the US patent office. Nobody related to this topic is my client in even that capacity.