The primary reason for the change, say sources familiar with Apple's plans, is to support sophisticated new multitasking APIs in iPhone 4.0. The system will now be evaluating apps as they run in order to implement smart multitasking. It can't do this if apps are running within a runtime or are cross compiled with a foreign structure that doesn't behave identically to a native C/C++/Obj-C app.

"[The operating system] can't swap out resources, it can't pause some threads while allowing others to run, it can't selectively notify, etc. Apple needs full access to a properly-compiled app to do the pull off the tricks they are with this new OS," wrote one reader under the name Ktappe.