How interactive content will play on the Kindle e-reader in a world awash with all sorts of tablets remains to be seen, but Amazon has now opened up limited beta access to the Kindle Development Kit (KDK).

This provide what Amazon calls 'rich APIs, tools, and documentation to help you create active content on Kindle'.

Application will run natively in Java, and have access to Amazon's Whispernet mobile network.

Voice over IP functionality, advertising, offensive materials, collection of customer information without express customer knowledge and consent are, unsurprisingly, prohibited.

Data charges

Details have also been released about the business model will work with respect to applications that use online features; something Amazon calls active content.

These must be smaller than 100 MB. Applications larger than 10 MB will not be delivered wirelessly but will have to downloaded from the Kindle Store to a computer and transferred to the user's Kindle via USB.

In terms of net revenue for active content, it will be split 70:30 between the developer and Amazon (as per usual), but Amazon will charge $0.15 per MB downloaded.

This is charge is waived in the case of free applications that are smaller than 1 MB and use less than 100 KB per user per month of wireless data, where Amazon will cover the delivery and maintenance costs.

With one-time purchased content, customers will be charged once when purchasing active content and the content must use less than 100 KB per user per month in terms of ongoing wireless usage.

Content that uses monthly subscriptions will see customers charged once a month for their active content usage.

Amazon takes its cut of $0.15 per MB downloaded in these latter cases.

Developers can find more details and sign up to become a beta developer at the KDK Portal.