"Nokia will use the best browser for the job. Currently, we cannot make a full-featured and integrated browser with WebKit in mobile. But with Mozilla, we do not need to do anything, we can take existing models and API's which are available. Also, NPAPI support is already in the Gecko web rendering engine. They are also concerned that WebKit is to some extent controlled by Apple, who are in competition to Nokia with their iPhone." (hat tip to Chris Blizzard)
WebKit is an open source web browser engine. WebKit is also the name of the Mac OS X system framework version of the engine that's used by Safari, Dashboard, Mail, and many other OS X applications.
But the big deal is that the coders that invented the underlying layers that power Konqueror, some Nokia browsers, Abrowse, Safari, Adobe's Air, and now Epiphany and a few other projects that are in the works, are now back in the fold.