I'm using the qtreactor in a GPL-but-unreleased PyQt 4.1 application of my own, and have not found any problems whatsoever with the integration of the Qt Twisted event loops. It's really a pretty slick combination. As an example and a contribution, I offer the following (GPL'd) module: http://deadbeefbabe.org/paste/1996 (syntax-highlighted version), http://foss.eepatents.com/misc/qt-twisted-dialog.py (source). It allows you to construct a non-blocking modal dialog, immediately obtaining a deferred to the user's eventual input. As an aside, I would be interested in people's viewpoints about whether the Qt reactor is suitable for Twisted's MIT-style license, given that it doesn't actually import any Qt code itself. It leaves that step up to the user with the installation of a reactor into the Qt application object. As every Qt user probably knows, the Qt library itself is dual-licensed under either the GPL or Trolltech's proprietary license. Best regards, Ed