The press release is finally out: "Nokia develops a new browser for Series 60 by using open source software." From the press release, "the Series 60 browser will use the same open source components, WebCore and JavaScriptCore, that Apple uses in its popular Safari Internet browser."
I'm so glad that's finally public information. It's another one of those projects that I've been super excited about, but couldn't tell anyone. Congrats to the teams involved for making it happen!
[Dave Hyatt (on the Safari team at Apple), Matt Croydon, and MacRumors have also posted about the news.]