When the in app purchasing launched earlier this year, iPhone developers offering up free apps couldn't join in on the fun. But Apple has now made this happen.

According to a recent e-mail circulated by the iPhone Developer Program, Apple informed developers that they could not build free applications that could allow people to purchase something within. 

"In App Purchase is being rapidly adopted by developers in their paid apps. Now you can use In App Purchase in your free apps to sell content, subscriptions, and digital services," Apple notes.

This opens the doors for developers to submit one application that acts as a trial version, but can be upgraded after downloading to the full version. Apple says in its e-mail to developers that this could cut down on iPhone app piracy that's been going on since developers can verify that the content has been purchased.

via TUAW