"You may have remembered that in the past I've talked about some of the development of 64-bit applications on Mac OS X. The gist of it is that Apple changed their position on supporting 64-bit Carbon, the library we depend on for running Qt GUI applications. It became obvious early on that Apple wasn't going to change their position on this, so it left us with two choices: keep Qt Carbon-only and forego 64-bit support, or create a port of Qt that used Cocoa as its backend. Naturally, since we already support 64-bit on the other platforms and since the idea of using Qt is to help insulate you from changes such as this, we decided on the latter option. It did mean that we had a bit of work ahead of us, since we had to re-write some of the internals of Qt (particularly widgets and events), but most of the other modules were already there. I'm happy to say after a bit of work, we've made progress and we're proud to offer an alpha for curious people that want to try 64-bit applications on Mac OS X 10.5."