Third-party software developers can create Web 2.0 applications to run on Apple's forthcoming iPhone, company CEO Steve Jobs said Monday.

[ For the latest from the show, read Tom Yager's Enterprise Mac blog. ]

Jobs told an enthusiastic audience at Apple's Worldwide Developers Conference 2007 in San Francisco that developers could write applications that work and look like iPhone applications from Apple, including those for making calls, sending e-mail, and other functions.

The iPhone, a combination cell phone, Web browser, and video and music player, goes on sale June 29.

Developers will be able to create applications for the iPhone by using Web 2.0 programming tools such as AJAX (Asynchronous JavaScript and XML) and taking advantage of the full version of Apple's Safari Web browser incorporated into the devices. A separate, special software developer kit is not needed, Jobs said.

The software development announcement was the last item in a 90-minute keynote address devoted mostly to the new OS X version 10.5 operating system, code-named Leopard and scheduled for release in October. Jobs highlighted 10 of what he said were 300 new features for Leopard, an upgrade from the present Tiger OS. Leopard will sell for $129.

Also, Apple's updated Web browser, Safari 3.0, will be available to run on Windows Vista and Windows XP, Jobs said. Apple is releasing a public beta of Safari 3 for Mac OS X and Windows Monday, said Jobs.

Jobs said the company took a cue from its experience enabling the iTunes Web music and video store to run on Windows. Safari has only 5 percent of the market for Web browsers, compared to 78 percent for Windows and 15 percent for the Firefox browser. Jobs said running on Windows could increase Safari's market share.

Some in the audience of an estimated 5,000 literally oohed and ahhed as Jobs demonstrated new features of Leopard, including a feature called Stacks. In order to reduce clutter on computer desktops, Stacks can hide application icons behind the main icons on the application dock at the bottom of the screen. Click one of those icons, and others behind it shoot up toward the top of the screen in a stack.

Leopard will also run 32- and 64-bit applications side by side, Jobs said.

He also demonstrated a new Leopard feature called "Cover Flow" in which images of files flip quickly across the screen from side to side, allowing users to find the image they want, click on it and see that file open up full screen.

"This is an amazing way to find things, and it's incredibly useful," Jobs said.

Apple said in April that it would delay Leopard's launch until October because it was devoting time and energy to bringing the iPhone to market.

Apple is gaining attention because of TV commercials featuring a character called "Mac" and another called "PC." In a video prior to Jobs' keynote, John Hodgman, the comedian who plays the dim-witted Windows PC user in the commercials, appeared onscreen wearing Jobs' trademark black turtleneck and blue jeans, trying to pass himself off as Jobs. "I'm quitting," he declared, saying that he was closing down Apple because the Windows Vista OS was just too popular.

"They have sold tens of ... dozens of copies," Hodgman said.

This story was corrected on June 12, 2007.