Because of Twitter’s recent enforcement of token limits, we only have a limited number of tokens available for Tweetbot for Mac. These tokens dictate how many users Tweetbot for Mac can have. The app’s limit is separate from, but much smaller than, the limit for Tweetbot for iOS. Once we use up the tokens granted to us by Twitter, we will no longer be able to sell the app to new users. Tapbots will continue to support Tweetbot for Mac for existing customers at that time.
Oh yea, Twitter loves it’s users :(