Cesar has release an alpha release of WebRunner deployed as a Firefox extension and launched using Firefox as the runtime. That’s right, delivered using Firefox’s extension mechanism and launched using Firefox’s runtime. No XULRunner needed for this deployment. It seems to work on Linux, but we need to make some changes for Windows and Mac. Also, check out some of the WebRunner Planning discussion to see what ideas are being kicked around.
As Cesar says, we think this is a possible direction for WebRunner. We could do more. We’re looking for feedback. We are still working on the standalone XULRunner version of WebRunner and should have a new release out soon.