Apple said it will allow developers of applications for its iPhones and iPads to use software such as Adobe Flash, a move that lifted Adobe’s share by 12 per cent on the promise of higher sales.

Gleacher & Co analyst Brian Marshall said Apple was feeling pressure from app developers. Because of Apple’s restrictions, many developers had to spend time and money to build separate versions of apps to work on both iOS and Google Inc.’s Android smart phone platform, which has surged in popularity.

“What spurred this on was the uproar from the growing iOS developer base,” Mr. Marshall said. “People liked using Flash, and now they’ll be able to use a bunch of different technologies.”

The two companies have a long-running feud over Apple’s refusal to allow its devices to play videos powered by Adobe's flash software, one of the most popular on the Web. Apple said the tool suffered from, among other things, weak security. Apple chief executive officer Steve Jobs has called the program “buggy.” Adobe's founders have said Apple stifles innovation.

The U.S. Department of Justice reportedly looked into the ban for possible antitrust implications.

“We are relaxing all restrictions on the development tools used to create iOS apps, as long as the resulting apps do not download any code,” Apple said in a press release. “This should give developers the flexibility they want, while preserving the security we need.”

Even though iPhone and iPad users likely still won’t be able to view Flash content on their Web browsers, Apple is now allowing developers to use Flash tools in their design process. The move is a huge boon for Adobe, which is no longer shut out of the world’s most popular apps store.

Besides the threat of an antitrust investigation, there are at least two other likely reasons why Apple backtracked on its previous position. The first is games. As smart phones become more powerful, the number of smart phone game apps is quickly growing. However, many games are designed using cross-platform tools, so designers can build games for more than one kind of smart phone. By previously limiting the use of such tools on its platforms, Apple effectively outlawed some of the most popular game-building software available, making life more difficult for many major game studios.

Apple’s policy change also comes at a time when the company is facing stiff competition from companies such as Google Inc. and Research in Motion Ltd. Google’s Android smart phone operating system now powers some of the most popular devices on the market, including units from HTC Corp. and Motorola Inc., and arguably represents the biggest threat to the iPhone’s popularity with consumers. RIM has shifted its focus to the consumer market, most recently with the release of its newest phone, the Torch. In effect, Apple’s more relaxed app rules give developers less incentive to abandon the company’s mobile devices for its competitors.

In addition to relaxing its development rules, Apple also publicly released the guidelines it uses to reject certain apps. The company had previously faced stiff criticism for what was seen as a fairly arbitrary rejection policy – Apple’s policy of rejecting certain content it deemed offensive or pornographic, in particular, opened the company to allegations of censorship.

Although Apple’s guidelines are now available for public review, their content indicates the company’s rejection policies will remain largely subjective.

“We will reject Apps for any content or behaviour that we believe is over the line,” the document states. “What line, you ask? Well, as a Supreme Court Justice once said, ‘I'll know it when I see it.’ ”