Opera Software, who distributes the Opera browser across multiple platforms, is apparently being blocked from becoming a version for the Apple iPhone by Apple not allowing the Opera iPhone app into the Apple App Store.
Mr. von Tetzchner said that Opera’s engineers have developed a version of Opera Mini that can run on an Apple iPhone, but Apple won’t let the company release it because it competes with Apple’s own Safari browser.
This could be something to do with the Javascript interpreter, or Apple restricting applications which compete with their built in iPhone applications such as Safari. With Apple restricting apps, especially alternative browsers, iPhoner will probably not be seeing an alternative such as FireFox anywhere on the Apple App Store very soon.
Source — nytimes