SAN FRANCISCO (AP)--Adobe Systems Inc. (ADBE) is contributing some of the computer code behind its widely used Flash player to the Mozilla Foundation so that it can be improved upon and blended into an upcoming version of Mozilla's Firefox Web browser.

The donation, to be announced Tuesday at the Web 2.0 conference in San Francisco, represents the largest contribution of code to Mozilla since the Mountain View-based foundation's 2003 inception. The code covers the scripting language in Adobe's Flash software, which millions of people use to view online media and other dynamic applications delivered over the Internet.

San Jose-based Adobe, best known for its Photoshop and Acrobat programs, picked up the Flash software as part of its $3.4 billion acquisition of Macromedia Inc. last year.

With the Mozilla contribution, Adobe becomes the latest major software company to throw its support behind open-source software - a concept founded on the belief that a global community of independent programmers can improve computer code by freely sharing their work.

Both Microsoft Corp. (MSFT) and Oracle Corp. (ORCL) have announced expanded support of open-source software during the last two weeks.

Mozilla has set up an open-source project called "Tamarin" to manage the future contributions to the scripting language code from Adobe. The project will be managed jointly by developers from Adobe and Mozilla.

"By working with the open-source community, we are accelerating the adoption of a standard language for creating and delivering richer, more interactive experiences that work consistently across PCs and mobile devices," said Kevin Lynch, Adobe's chief software architect.

The improvements eventually will be incorporated into the Firefox browser, probably in an upgrade scheduled for the first half of 2008, said Frank Hecker, the Mozilla Foundation's executive director. Mozilla is counting on the improvements to make many Web applications run more smoothly and quickly in Firefox.

The Flash player will continue to work on Microsoft's dominant Internet Explorer browser.

In just a few years of existence, Firefox has emerged as the most popular alternative to Internet Explorer, which commands an 86% share of the market, according to WebSideStory. Two years ago, Explorer held a 93% share. Firefox's share stands at about 11%.