Microsoft has given its most ringing endorsement of open source Web browsers to date with chief executive officer Steve Ballmer not ruling out adopting such technology as an alternative to its own popular Internet Explorer, saying it is "interesting".

In Sydney to speak at a Power to Developers event, Ballmer ignited the audience with his powerful "Developers! Developers! Developers!" chant, but was surprised to hear a question about open source browser adoption from one of his student constituents.

"Why is IE still relevant and why is it worth spending money on rendering engines when there are open source ones available that can respond to changes in Web standards faster?"

"That's cheeky, but a good question, but cheeky," Ballmer said.

Indeed it is. If I was a Microsoft share holder I would want to know why Microsoft is sinking so much money into its own Web browser rendering engine when there are others available for free. Good thing the chairs in Sydney's Exhibition Centre are all bolted down.

Ballmer began his answer philosophically, saying Microsoft will need to look at what the browser is like in the future and, if there is no innovation around them, which he thinks is "likely", Microsoft may still need its own browser because of proprietary extensions that broaden its functionality.

"There will still be a lot of proprietary innovation in the browser itself so we may need to have a rendering service," he said.

Then came the startling revelation that Microsoft may also adopt an open source browser engine.

"Open source is interesting," he said. "Apple has embraced Webkit and we may look at that, but we will continue to build extensions for IE 8."

Ballmer also admitted Microsoft got delayed with the transition from IE 6 to IE7 during the development of Longhorn, which became Vista. "But I don't what to go there."

Developers want money

Another question arose from the recent success of Apple's App Store and Facebook for helping independent developers make money via the host vendors application delivery mechanism. Ballmer wants to do more here for Microsoft developers.

"Making money is a good thing and with some of the competitive opportunities I don't think anyone is making any money," he said. "Some good work is being done with Facebook and the iPhone where it's easy for developers to distribute applications. It's easier to get exposure. Not much money is being made, but giving developers a way to get more visibility of their code is a good idea.