Looking at the page with Safari and plugins and Javascript enabled, the script shows the flash content as intended. If I disable Javascript, the alternate content shows, again as intended. If I turn off plugins, however, the flashcontent area is blank. I tried using so.setAttribute("redirectUrl", "http://www.example.com");, but it didn't work. Perhaps that kicks in only if using Express Install in the Flash file. For this purpose, the Flash content is fun, but not important: if a viewer has turned off Flash or doesn't have a Flash player, I just want the page to load the alternate content.
This is a bug in safari (not sure if they recognize it as such, though) - basically javascript reports incorrectly that the browser has the Flash plugin, so swfobject writes the swf code to the page, but safari should not be reporting that flash is available. nothing we can do about this one other than harass apple into fixing it.
Whether or not it's a bug may be a matter of semantics. Even when I uncheck "Enable plug-ins," I still do literally have the plug-in. Of course that's like asking someone, "Do you know what time it is?" and the answer comes back, "Yes."