In concert with the release of Windows Phone App Studio, Microsoft has announced it is loosening the restrictions around the unlocking of phone for developer usage (i.e. the ability to side load an app). Previously getting a phone developer unlocked required a Dev Center account, which required a $99 annual subscription. However, from today a free option, open to any developer, will also be available.

Dev Center still provides the best option as it allows you to register up to three devices and side load up to ten apps. The free option will be limited to registering a single device and side loading two apps, but should be enough to get developers started, and encourage the testing of apps on real devices, rather than the PC-hosted emulator.

Those looking to publish an app to the Windows Phone Store will still need to sign up for a Dev Center account. As noted above the standard price is $99, but Microsoft is currently running a "Summer Break" promotion, which reduces the cost to $19 (available until August 26th).

The move to ease developer unlocking restrictions may have been prompted by the release of Windows Phone App Studio, but it also has a wider significance. It will make it much easier to side load apps, which may encourage the growth of "home brew" apps. These apps are typically released by those who are unable or do not want to use the formal publishing process, or for apps that might not pass the Windows Phone Store approval / quality assurance process (e.g. taking advantage of a work around to give access to private API / unintended functionality).

More information on the new unlocking process is available in this Windows Phone Developer Blog post.