You can use a scripting language if it does not load any code. This is not an apple with a scripting language, the problem with Angry birds, for example, is using ( lots ) of Lua code. 
If you try to download the code and execute it, Apple will reject your application. Although this is a gray area. For example, "when does something become code?" As an example, you can download a new level package for your game, if then the level is defined in XML files. But let's say, for example, you are using your own file format, not XML, for more functionality. At what point does your code stop just to identify parts of the game and become a code?
As with many regulatory documents, there are gray areas, even with things forbidding Apple (downloading code), however you should not have problems using the scripting language.
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