Qt 4.5 will be available under the LGPL

· by Steve · Read in about 2 min · (395 Words)

I’m on the Qt (owned by Nokia now) mailing list since I have a commercial license for a client project, and I got a very interesting email today, telling me that on its release in March 2009, Qt 4.5 will be available under the LGPL.

This is really big news. Up until the current Qt 4.4, your only licensing options are a per-seat and per-platform commercial license (which adds up if you have multiple developers and multiple target platforms, which you will do if you’re using Qt anyway), or alternatively the free option which means you use it under the GPL - meaning all your own code has to also be GPL, with an exception that allows you to publish / use software under other open source licenses too, but nevertheless it all has to be public. There’s a pretty big chasm in between these two options that in my experience a lot of projects fell into.

So, offering an LGPL option from Qt 4.5 is a major development. Qt is a really excellent library, the best cross-platform, native code widget set I’ve seen, but the licensing cost often put people off; this changes everything. I’m actually quite surprised they’re going this far - I think just changing the commercial licensing structure to be a little less multiplicative would have made a lot of people happy, but the LGPL option really turns things upside down. Essentially it means that you get all the cost benefits of the GPL version, except there’s a ‘fire break’ of open source responsibility between Qt and your application, meaning a lot more people can consider it. Nokia’s stated aims are:

  • facilitate wider adoption of Qt across industries, desktop, web and embedded platforms
  • establish Qt as a de facto standard for application development
  • receive more valuable feedback and increased user contributions to ensure that Qt remains the best-in-class, cross-platform framework
  • extend Nokia‚Äôs existing platform commitment to the open source community

I’m pretty sure this move will achieve all of those goals. It may well take a little wind out of the sails of wxWidgets, which in my experience never seemed quite as polished as Qt, but the licensing was much more favourable - although of course the wxWidgets project is still a lot less ‘corporate’, so will continue to have an appeal from feeling a bit more open.

Interesting times anyway!