Users of the iPhone 3G can now download new browsers from Apple's App Store, but don't look for big-name alternatives to Safari any time soon.

When Apple unveiled its App Store last year, it had certain restrictions on what developers could create. One of those limitations was that no app could duplicate existing functionality of the iPhone, which is why there hasn't been an alternative music player or browser yet.

Over the last few days, four browsing applications have been approved by Apple and are available for download. These apps get by Apple's terms of service because they just put a different user interface on top of the iPhone's WebKit rendering engine.

The apps range from free to $1.99, and they are essentially still Safari but with added features or an altered UI. Edge Browser gives users more real estate by removing the navigation bar, Incognito lets users browse without leaving a history, WebMate: Tabbed Browser makes clicking multiple links simple, and Shaking Web uses vibration-reduction technology to make reading Web pages easier while moving.

This move probably doesn't pave the way for the likes of Opera Mini or a mobile Firefox on the iPhone 3G, as they are based on different rendering engines.

"What has been released thus far are skins on top of Safari, so we are not certain if Apple has relaxed its policy," an Opera spokesman said in an e-mail. "Our goal remains, as always, to make our browser available on as many platforms as possible. However, Opera is at this time not available for the iPhone."