As the app store wars rage on, web giant Microsoft has drawn its line in the sand, releasing a list of what it will and won’t allow Windows mobile applications sold in its store to do.

Windows Marketplace is set to launch in the fourth quarter of this year and the Redmond firm looks like it will be every bit as draconian as Apple when it comes to vetting the apps for distribution.

On the list of prohibited application types are those that enable VoIP over the mobile network, which suggests VoIP over wifi is fine; apps that sell or promote mobile voice plans or replace or modify the default dialler and messaging interfaces; apps that change the default web browser, search client or media player or run outside of Microsoft runtimes; and apps that publish user data or location information without permission. But the big no-no is any application that promotes or features rival app stores, which might put operators in something of a predicament if they want to launch their own app stores. Never mind the handset vendors.

The app store will launch alongside version 6.5 of the Windows mobile platform which, from what telecoms.com has seen of it, will see the company push even further into the consumer space with a flashier user interface and easier access to information by reducing the configuration and number of clicks required.

In related news, it looks like rival Apple might be preparing to loosen its rules through the introduction of parental controls for applications in version 3.0 of its iPhone operating system. Apps that have recently been rejected from the Apple App Store because of objectionable content can be resubmitted once new features become available, Apple has said, with strong suggestions towards parental controls.

Apple recently announced that consumers have downloaded one billion applications since its launch in August 2008.

Apple’s application marketplace, which is largely responsible for setting an industry bandwagon in motion, has more than 35,000 applications available today in 77 countries.

This summer, the forthcoming iPhone OS 3.0 software update will provide developers with over 1,000 additional APIs, enabling app store purchases from within applications, peer to peer connections, control of accessories from within apps, as well as Push Notifications.