Basically, the main toolkit for the Maemo platform will become Qt instead of Gtk+, with Gtk+ becoming a community maintained part of Maemo. However, all of the underlying technologies will still be GNOME-centric, such as glib, dbus, gvfs, bluez, telepathy, avahi, gstreamer, gconf, and so on.
The news was announced by Maemo/Nokia Open Source Marketing Manager Quim Gil during his keynote at the Gran Canaria Desktop Summit. "Maemo Harmattan will base its application framework in Qt while keeping most of the Fremantle middleware based on GNOME technologies," he writes on his blog, "The goal is to offer an open, efficient and compelling Linux mobile stack with a cross-platform Qt API used also by Symbian and available in other mobile and traditional operating systems."
GNOME developer Vincent Untz also writes about the change on his blog. "So while the move to Qt is a logical move from Nokia, it's good to see that Nokia stays firmly committed to GNOME Mobile. It's actually quite amazing to see that what we built there is attractive to a big industry player like Nokia (and, well, a bunch of other players)."
The first devices based on the new Maemo platform are still a while off, as this year's Nokia N900 (a rumoured device) is still supposed to be based on Gtk+.