After months of speculation about its ambitions in mobile telephony, Google on Monday revealed its plans... would not include a so-called gPhone.

Instead of hardware, the search conglomerate introduced Android, a Linux-based open development software platform for mobile phones, and a broad alliance of technology companies dedicated to building applications and devices with Google's software.

"This partnership will help unleash the potential of mobile technology for billions of users around the world," said Google chairman and chief executive Eric Schmidt in a statement. "A fresh approach to fostering innovation in the mobile industry will help shape a new computing environment that will change the way people access and share information in the future. Today's announcement is more ambitious than any single 'Google Phone' that the press has been speculating about over the past few weeks. Our vision is that the powerful platform we're unveiling will power thousands of different phone models."

Google's ambition is nothing less than prying the telecom industry open and merging it with the Internet. "The openness of the Internet is starting to impact the relatively closed environment of the mobile handset makers," said Mark Kirstein, founder and CEO of MultiMedia Intelligence, a technology market research firm.

"Android is the first truly open and comprehensive platform for mobile devices," said Andy Rubin, Google's director of mobile platforms, in a blog post. "It includes an operating system, user interface, and applications -- all of the software to run a mobile phone, but without the proprietary obstacles that have hindered mobile innovation. We have developed Android in cooperation with the Open Handset Alliance (OHA), which consists of more than 30 technology and mobile leaders including Motorola, Qualcomm, HTC, and T-Mobile."

Google said that the OHA plans to release a software development kit next week. Ethan Beard, director of new business development at Google, who helped set up the partnerships behind the OHA, said that the SDK would rely on the Apache 2.0 license, which allows developers to create proprietary applications on top of the Android platform without being forced to make their application code publicly available.

Google's "open," then, is open with an asterisk. But it's certainly more open than other phone platforms to date.

Android also promises to open a new revenue stream from mobile advertising, which to date has been more of a trickle. "Mobile advertising is still a tiny little industry, but this is a major development," Kirstein said.

Google has a long list of partners for this alliance: Aplix, Ascender, Audience, Broadcom, China Mobile, eBay, Esmertec, HTC, Intel, KDDI, LivingImage, LG, Marvell, Motorola, NMS Communications, Noser, NTT DoCoMo, Nuance, Nvidia, PacketVideo, Qualcomm, Samsung, SiRF, SkyPop, SONiVOX, Sprint Nextel, Synaptics, The Astonishing Tribe, Telecom Italia, Telefonica, Texas Instruments, T-Mobile, and Wind River.

But it's also worth noting who's absent from the list: Apple, AT&T, Microsoft, Nokia, Palm, Research in Motion, Symbian, and Verizon. Apple spokesperson Natalie Kerris said about Google, "Clearly they're an important partner and today's announcement doesn't change that." She declined to speculate about whether Apple would join the alliance, but pointed out that Apple CEO Steve Jobs has said that Apple plans to make the iPhone a more open platform for developers through the release of a software development kit early next year.

Microsoft's Scott Rockfeld, group product manager for Microsoft's Mobile Communications Business, sounded less upbeat. "Really, what we heard wasn't surprising," he said, referring to the conference call detailing the announcement. "It's not new or revolutionary, either. It's kind of what Windows Mobile has been doing for the past five years."

Asked whether Microsoft would consider joining the alliance, Rockfeld chuckled and replied, "We weren't invited." And he added that Microsoft already has an alliance of its own that includes 48 equipment makers, 160 mobile operators in 55 countries, and thousands of independent software vendors.

Verizon was more circumspect. "We welcome the support of Google, handset makers, and others for our goal of providing more open development of applications on mobile handsets," the company said in an e-mailed statement, noting that it hasn't ruled out joining the OHA. "In today's wireless marketplace, companies compete fiercely by offering customers what they want: reliability, great customer service, and innovative and compelling products and services. Our competitive marketplace is a tremendous laboratory for innovation, where great ideas bubble to the top and resonate with customers."

Jason Mackenzie, VP of HTC America, said that his company's participation in the alliance wouldn't have any impact on its relationship with Microsoft. "Microsoft will continue to be a big part of who HTC is and a big part of our future projects," he said, noting that HTC produced 75% of Windows Mobile handsets this year and that it expects to grow that share next year.

Mackenzie said that HTC plans to be first to market with an Android-based phone in the second half of 2008. He declined to provide details about the device and said that this particular device wouldn't involve a mobile ad revenue sharing arrangement with Google. As to whether future models might, he said it was too soon to tell.

"I think the industry is ready for open," said Mackenzie. "The OHA alliance is a step in that direction."

"We think this could be game-changing," said Beard from Google. "We see it accelerating developers to create interesting and innovative mobile Web applications. The more interesting things that are going on the mobile Web, the more people will use the devices."