Since rolling out the first Kindle electronic reader two years ago, Amazon.com has kept the Kindle platform closed to outside developers. Now Amazon is taking a page from Apple's playbook and opening a Kindle app store. The move comes less than a week before Apple is expected to unveil its much hyped tablet computer, which is targeting the e-book market.

Here's how Amazon describes the Kindle app program:

Today, Amazon announced that it is inviting software developers to build and upload active content that will be available in the Kindle Store later this year. The new Kindle Development Kit gives developers access to programming interfaces, tools and documentation to build active content for Kindle--the #1 bestselling, most wished for, and most gifted product across all categories on Amazon.

More:

Starting next month, participants in the limited beta will be able to download the Kindle Development Kit, access developer support, test content on Kindle, and submit finished content. Those wait-listed will be invited to participate as space becomes available. The Kindle Development Kit includes sample code, documentation, and the Kindle Simulator, which helps developers build and test their content by simulating the 6-inch Kindle and 9.7-inch Kindle DX on Mac, PC, and Linux desktops.

Ian Freed, Amazon's vice president of Kindle at Amazon, tells the New York Times he envisions apps like "calculators, stock tickers and casual video games" for Kindle and said publishers could create a "new breed" of electronic books such as "searchable travel books and restaurant guides that can be tailored to the Kindle owner’s location; textbooks with interactive quizzes; and novels that combine text and audio."

Opening up the Kindle platform is a big change of pace for Amazon, which has been very secretive about its Kindle business, and will raise the stakes in its competition with Apple. Developers will be limited by the current Kindle design — including the slow-moving, black-and-white screen and basic web browser — though the company is likely developing new Kindles with more advanced features.

Amazon is making a bunch of Kindle-related announcements as Apple's much-hyped Jan. 27 media event approaches. Amazon said yesterday it would give authors and publishers a bigger cut of e-book sales through its Kindle publishing platform.

In recent days, reports have surfaced that Apple is in talks with publishers like HarperCollins about putting e-books on the new tablet computer — and letting publishers set their own price. Amazon has clashed with publishers over its heavy discounting of e-books at $9.99 or lower, which critics fear will devalue books in the eyes of consumers.

Amazon says it will split Kindle app revenue 70-30 with 70 percent going to the developer and 30 percent going to Amazon "net of delivery fees of $0.15 / MB." The apps can be free or sold to customers for a one-time purchase price or on a monthly subscription basis. Amazon is not allowing Kindle apps with "Voice over IP functionality, advertising, offensive materials, collection of customer information without express customer knowledge and consent."

The company said Handmark and Sonic Boom are already developing Kindle apps, and EA Mobile is interested.

I was struck by Amazon's change of tone on opening the Kindle platform.

“We knew from the earliest days of the Kindle that invention was not all going to take place within the walls of Amazon,” Freed told the Times. “We wanted to open this up to a wide range of creative people, from developers to publishers to authors, to build whatever they like.”

When I asked Freed about opening Kindle to outside developers in Nov. 2008, he was a lot more circumspect.

"Over time it might be something we look at, but right now we’re focused on creating a great reading experience and I think we have the applications on the platform that do that," Freed said at the time. "But supporting a wider ecosystem for applications is nontrivial and we want to make sure we’re serving our reading customers first and foremost and then we look at other things."

Follow my updates on Twitter.