There are also reports of XML having been added to Netscape which should particularly interest you. The point isn't that everyone will want to download the source and modify it. After all, most linux users don't modify their kernal themselves. The point is that the people that want to add new features can. Of course, I don't personally plan on using any versions of Navigator except for the Netscape one.
People are busy busy busy.
They want to double-click and get going. My bet is that the developers would have ranked the free source code much higher than non-developers. At a certain level, Frontier's source code is free. Steal parts and use them in my own scripts. Being a UserTalk developer, this free source code is really handy for me.