> Apps that use the Gecko platform, use it directly, using internal APIs (apps like Fennec and Songbird already do this).
Songbird certainly doesn't; I doubt Fennec does, either. The whole not being part of libxul thing and all.
> This obviously means they need to keep up to date if they are out of tree, or that they should be in-tree (in the mozilla-central repo).
Except that people are _against_ putting more things in m-c - see pyxpcom, for example, which used to be in-tree before hg, or ipccode which isn't either.
> (2) to provide a very simple, very stable, very high-level API, *not* for embedding
But what people _want_ is embedding, because they want to be able to control the browser - where it navigates to, when it tries to launch the system browser instead for off-site links, what context menu gets shown. Just slamming a remoted Firefox bitmap in doesn't provide enough controls. At this point, of course, any new projects would be better off using WebKit (via Gtk/Qt/Cocoa bindings) or IE (IWebBrowser).