Inverting the Golden Cage, or a Gift to the Barbarian Hordes at Apple’s Gates.
The now-infamous iPhone / iPad SDK Section 3.3.1 reads:
“3.3.1 — Applications may only use Documented APIs in the manner prescribed by Apple and must not use or call any private APIs. Applications must be originally written in Objective-C, C, C++, or JavaScript as executed by the iPhone OS WebKit engine, and [...]