Apple has placed restrictions on its iPhone SDK that bar developers from porting Adobe Flash and Mono applications to the iPhone.

Changes made to the terms of Apple’s iPhone Developer Program License Agreement on April 8 forbid cross-compiled applications. Apple’s decree reduces developer flexibility and potentially weakens competing runtimes or languages, said Al Hilwa, programmer director of applications development software at IDC.

The iPhone SDK’s APIs must now be used in the manner prescribed by Apple, and they cannot call private APIs; applications must be originally written in C, C++, JavaScript or Objective-C, according to the license.

Third parties, including Adobe and Novell, have released tools that translate code for execution on the iPhone. Adobe produces the Flash-to-iPhone cross-compiler, and Novell develops MonoTouch, a tool that brings .NET development to the iPhone.

Novell is reaching out to Apple for clarification on its intentions, and it will advocate for the license agreement to be amended prior to the release of Apple’s iPhone 4.0 SDK this summer, said Joseph Hill, product manager for MonoTouch at Novell. Apple did not return a request for comment.

“While this restriction can be seen in the prism of the Apple and Adobe relationship around Flash, this is not just about Adobe, but potentially a problem for every developer runtime or language that wants to hold on to developers and maintain its longevity,” said Hilwa.

“It is about programmers maintaining their livelihood. Probably even more importantly, it is about the flexibility to evolve computer science and software development.”

Apple’s decision to exert more control over developers could preclude it from evolving its own platforms in the future when new languages or interfaces grow in popularity, Hilwa added.