Outsider is a Windows Phone community app from Liquid Daffodil, who also brings us the Twitter client glƏƏk! and the lockscreen utility Locksider. We've been notified by the developer that a glitch in the Windows Phone Store is requiring those who have already purchased Outsider to re-purchase the app.
Microsoft has been alerted of the issue but in the meantime, Liquid Daffodil has made Outsider free to avoid users from having to re-pay for the app. The change is already live and should be reflected in all regions in a short bit. The free offer is only for the next 48 hours though.
You can find Outsider here in the Windows Phone Store and it is compatible with both Windows Phone 7.x and 8 devices. And if you're already a fan of the Outsider and need a little help with the Easter Eggs hidden throughout the app, check out "The Outsider Uber Guide for Noobs". It should get you pointed in the right direction.