Xcerion is one of those strategically important start-ups whose vision could make a big difference in the operating system wars of the future.

The Swedish company is developing a “cloud OS,” or one that does its computing not in the desktop but in the Internet-connected cloud. Today, the company is releasing an authoring tool that makes it easy to create applications for its operating system, dubbed icloud.

The significance is clear, as I wrote in a story for the San Jose Mercury News. Microsoft has dominated computing for decades with its desktop-focused OSes. Google wants to supplant Microsoft by embedding more applications such as Google Docs in the cloud. But it doesn’t have a true cloud OS, which makes it reliant on the hybrid model of “Google in the cloud, Microsoft in the desktop.” Xcerion has just the kind of cloud OS that Google needs to go to war with Microsoft.

Those two titans aren’t the only ones who have a stake in the “cloud versus client” OS battle. Google and IBM are collaborating on cloud computing research. Other cloud OSes include YouOS and Laszlo Webtop. Xcerion released its first beta version last September.

The company says in a release today that the new tool, dubbed Visual Application Designer for icloud, makes it easy to create applications for its OS. Those applications include scaleable apps, widgets, or mashups — all created through a drag-and-drop interface.

The beta version of the tool is available immediately. By making it available for free, the company hopes that third parties will begin to create applications such as the Office-like email, calendar, word processing, presentation, and other productivity apps needed to get any new OS off the ground.

The company says that applications within icloud can natively work as collaborative apps without much effort on the part of the developer. The cloud OS is based on the XML software standard and runs in a browser. You install it on top of another OS — such as Linux, the Mac OS, or Windows Vista — and so to call it an “operating system” is a subject for debate. The OS uses only about 1.5 megabytes of code that downloads to a computer in about four seconds. It has the look-and-feel of Windows.

Under the business model described to me in February, the OS is free but the code is owned by Xcerion. If someone makes revenues from it, such as advertising or subscription fees, then Xcerion takes a 10 percent cut of the revenues.

The company and product are the brain child of Daniel Arthursson, who worked on the technology for icloud for more than seven years.  He founded Xcerion AB in 2001 and the company now has a few dozen employees in Linkoping, Sweden. The plan is to have 50 collaborative applications before the end of 2009.

It has raised $12 million in venture money from Northzone Ventures and others. Those “other investors” are very interesting. They include Lou Perazzoli, one of the original architects of Microsoft’s Windows NT operating system; John Connors, a partner at Ignition Partners and former chief financial officer of Microsoft; and Terry Drayton, founder and former CEO of HomeGrocer.com.