Apple cannot limit what you develop elsewhere, they can only place limitations on what you can do in their app store. Many, many games have cross platform versions.

I disagree that Android wouldn't be worth it (erm...so I mean that Android IS worth it haha). Android is growing faster than ever right now and it's quickly catching up to Apple with the number of apps, etc. If I remember correctly Android just recently surpassed iDevices in usage (according to an article I read on Engadget), and they are only going to become more popular. Especially once Android 2.2 comes out and improves app performance 2x-5x. Anyway, what I'm trying to say is that if it's even reasonably possible to do it, Spacetime should go for it!