The devs are already working on an official Android port, an unofficial one was made by an user who took money for it. A Apple app was discussed and rejected.

From the Powder Toy on Android topic:

"we still don't have a mac and have no will to get one just to make on app for cydia. I was thinking maybe cydia if anything, but I think it would easy, getting it to work for android was hard enough"
This is why there's such a low chance of this happening.

I'm pretty sure just purchacing the SDK is about $100...

EDIT: 99 USD... a year.

and even from there things get complicated and expensive very quickly.

A homebrew port would be interesting, GCC has had obj-c capabilities for a long time, and no sane man would want to use xcode (or so I have heard).

You can actually develop IOS apps from linux (not sure about windows) if you are willing to set up the toolchain, and are willing to do development without an emulator to test the code on (or maybe there is an open source one? I am not sure, I have not delved into this topic myself.)

Of course, there is no way in hell Apple would get over their ego and allow you to sell the result on the app store, since it is not being compiled with their toolchain. So this method would only allow you to distribute a homebrew version.

A link for anyone interested: http://www.saurik.com/id/4

there is one but i would have to remember the post hold on...

EDIT: ok found it but it's for android go HERE to find it.