iPhone users would definitely be familiar with the term jailbreak and if you don’t know why people do it , let me explain it in one sentence. People mostly jailbreak their device apps so that they can install and use unauthorized apps and most of those are available for free. But Apple and Sony are fighting against the jailbreakers of their device but it is almost impossible to stop developers from doing this.
But Microsoft will have a different strategy for their Windows Phone devices as recently it has been announced by dev of ChevronWP7 Labs will soon jailbreak for the WP devices and that jailbreak would be approved by Microsoft itself. This jailbreak would allow users who want to develop their aps and use it with their phones or distribute it to other jailbreak users.
This jailbreak service will not be totally free as ChevronWP7 teams would charge a few dollars through your paypal account but its cost would definitely be less then official developer’s license.