As reported on Daring Fireball, Apple’s new iPhone SDK 4.0 appears to explicitly ban apps made using cross-compilers (tools that allow you to create iPhone apps using other languages, APIs and third-party tools). This includes not only Adobe’s upcoming Flash-based Packager for iPhone tool, a central gem in the Flash CS5 crown, but also up-and-coming third-party tools like Titanium:

My reading of this new language is that cross-compilers, such as the Flash-to-iPhone compiler in Adobe’s upcoming Flash Professional CS5 release, are prohibited. This also bans apps compiled using MonoTouch — a tool that compiles C# and .NET apps to the iPhone. It’s unclear what this means for tools like Titanium and PhoneGap, which let developers write JavaScript code that runs in WebKit inside a native iPhone app wrapper. They might be OK. This tweet from the PhoneGap Twitter account suggests they’re not worried. The folks at Appcelerator realize, though, that they might be out of bounds with Titanium. Ansca’s Corona SDK, which lets you write iPhone apps using Lua, strikes me as out of bounds.

While Apple is certainly within their rights to decide how developers create iPhone apps — and developer enthusiasm for the iPhone OS is likely to only get stronger with the iPad in the mix — it’s another example of Apple’s tendency to wield its godlike power over the platform with a heavy hand. Oops, did we forget to mention we just invalidated a bunch of companies’ business models while you were all marveling over the new multitasking features? But then, it has always struck me as insanely dangerous to hang one’s fortunes on the grace of such a fickle overlord in the first place.

» New iPhone Developer Agreement Bans the Use of Adobe’s Flash-to-iPhone Compiler (Daring Fireball)

Update: Jon Gruber follows up with a very well-reasoned examination of the likely thinking behind Apple’s decision. The quick summary: it’s good for everyone but producers of third-party app-building software (and, of course, the developers who use it). For those who were hoping for a shortcut: time to crack open Objective-C for Dummies.