One burning question about Windows Marketplace for Mobile has been whether you will be able to purchase an app and use it on more than one phone. Granted, most people don't have a desk drawer full of Windows phones, but it's not unheard of to have a few in a household.

Computerworld reports via a Tech-Ed session that phones will have to be registered with the Marketplace, via Microsoft's Live ID system. But doing so will allow you to install an up on as many as five phones with a single purchase.

This is far from unheard of. You can purchase and load apps onto as many iPhones and iPod Touches as you want, provided that they're all under the same iTunes account. No biggie.

Even for Windows Mobile, it's not that huge a step. Most apps – not all – employ only a basic protection scheme. They're either limited in function under a "trial" basis or time out after a specified amount of time. (Kinoma Play is the first exception that comes to mind. It reports home to the mothership if you load it onto another phone.) But in most cases you can load the same app on a number of phones, provided you have the registration code.

The Marketplace will change that, which should please developers. And provided the authorizing of multiple phones is smooth and seamless, we're all for it. Devs deserve to be paid for their work.