SAN FRANCISCO, CA — The line between the Web, the home or office computer, and mobile computing just got blurrier, thanks to Monday’s release of AIR, a new software development system from Adobe Systems.Seven years in the making, AIR is the brainchild of Kevin Lynch, formerly a software developer for Macromedia and now Adobe’s chief technology officer. Adobe bought Macromedia in 2005. AIR grew out of Lynch’s desire to tie all of his projects and development environments together and take them with him wherever he went, so he could work on them when inspiration struck.

The product is underpinned by Adobe’s Flash multimedia software, which may be the most ubiquitous code in the world. It resides on almost every Web-connected personal computer in the world and allows users to play animations, stream videos and engage in e-commerce.

As its name implies, AIR is pervasive, invisible and free. It allows developers to work seamlessly from anywhere and on any device, and it draws information from every available resource, including the Web. Residing on the desktop as an icon, the AIR interface mimics a Web browser but does not require a browser in order to run.

The software already powers an eBay application called eBay Desktop. It also powers Adobe’s Buzzword, an online word-processing program. Salesforce, FedEx, eBay, Nickelodeon, Nasdaq, AOL and The New York Times Company also have developed AIR applications based on the product’s beta version.

A growing number of technologists believe distributed applications like AIR represent the future of computing, which is becoming more portable all the time. Intel plans to release a low-cost computing strategy called “Netbook” in the coming weeks, and the initiative is expected to give a boost to the production of inexpensive wireless computers that rely on Web-based data storage instead of on built-in hard drives.

AIR is not alone, although it is one of the most exciting offerings from a major software-development company. Mozilla, Sun Microsystems, Microsoft and Google all are toying with their own versions of “Web-top” operating systems, as are small firms that hope to make their names by creating “the next big thing.”

The popularity of Apple’s iPhone and other smartphones is credited with spurring increased interest in the space. Market researchers have said about 123 million of the devices were sold in 2007 alone. People rely on them for much more than communication, but in order to make them truly useful as “pocket computers,” software must be downsized and ported across the myriad platforms on which they operate. Lynch said that shift in mindset is the most significant development in the software industry since graphical desktops and icons replaced command-line prompts in the 1980s.

“We need to deliver an experience that is like the PC desktop [on mobile phones],” Qualcomm Chief Operating Officer Sanjay K. Jha told the New York Times. “At the same time, people are used to the internet and you can’t shortchange them.”

In creating AIR, Adobe is going head to head with Microsoft and its .Net environment. Although .Net has developed a following of about 2.2 million developers (compared to Adobe’s community of more than one million Flash developers), .Net hasn’t taken off quite as well as Microsoft had hoped — possibly because it appeared on the market somewhat earlier than people were willing to adjust their thinking about integration and security. That’s not the case anymore, Lynch told the Times.

“This is a battle for the hearts and minds of people who are building things,” he said.

The battle has been brewing for some time, and scrappy Adobe — which already owns the hearts and minds of creative types owing to its suite of graphics and publishing tools — doesn’t intend to lose. When Microsoft released Flash challenger Silverlight, the product got high marks for its ability to handle high-resolution video. Adobe quickly upgraded Flash in response. Now both companies are racing to develop the security enhancements that will make their respective products “the killer app.”

“Desktop integration is a mixed blessing. There is potentially a gaping security hole,” Brad Becker, whom Microsoft hired away from a lead designer position on the Macromedia’s Flash development team, told the Times. “We’ve learned at the school of hard knocks about security.”