Update: As my commentors have pointed out, I had a couple of errors. JulesLt has a really good overview of the OS X GUI and fills in a lot of my gaps here. Also, iTunes doesn't use Webkit. Thanks to cgervais for pointing that out (confirmation is here). Finally, jrobcet corrected me that Quicktime can be downloaded without iTunes. Although iTunes does require Quicktime.
It has always struck me as a little bit odd that Apple, the toast of designers everywhere, wouldn't get into the Rich Internet Application (RIA) game. You could argue that they're too busy counting the money from their iPod sales to care much about the fledgling RIA market and that may be the answer. But after doing some digging, there might be a more interesting (if unlikely) scenario - they're planning to leverage Quicktime as an RIA platform using the upcoming Core Animation for Leopard.
Now I talked about this with Scott McNulty, the head blogger over at The Unofficial Apple Weblog and he told me I was crazy, so take this all with a grain of salt. His usually astute reckoning was that Core Animation is just for Leopard and that it wouldn't ever be cross platform. But indulge me for a second.
You can no longer download
Quicktime and iTunes separately iTunes without Quicktime. They go together as a package and run on both Windows and Mac. I'm not sure what the marketshare is but it has to be significant. Within that bundle you have the tools for rich media (Quicktime), a solid browser engine (WebKit) and XML support. If you take a look at the packets coming over on iTunes, it's all XML. The XML is rendering the iTunes GUI. Now imagine if Apple bundled Core Animation into Quicktime and enabled very rich XML based applications that run cross platform and come from the company everyone loves to love.
Before you start following Scott by calling me crazy, take a look at recent changes in Quicktime 7. The live resizing? Interactive Animation support via Quartz Composer? If they have implemented parts of Xcode in Quicktime 7 what would prevent them from implementing a good chunk of Core Animation in the next version? And think about what a platform based on Quicktime brings: MPEG 4, DRM - it could be the ultimate rich, high-definition, interactive experience. Take a look at Spaces and Timeline, both built with Core Animation as well as the video over on Handras' blog. All of this in a package that comes from a company with a big reputation. The implication for both Adobe and Microsoft is a big one. Apple makes a pretty formidable third platform.
As farfetched as this sounds, I just don't see Apple sitting out this battle. Everyone in the world is talking about how experience is so important and what some would call the ultimate experience company can't just sit by as other companies one up them when it comes to web experiences. I'm going to be keeping an eye on MacWorld. We may just see the first inklings of an RIA strategy from Apple. And basing it on Quicktime makes a lot of sense.