Download of TweetRain 1.3 for Mac was on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The program is included in Communication Tools. The actual developer of this free Mac application is b123400. We recommend checking the downloaded files with any free antivirus.
From the developer:
TweetRain displays your Twitter timeline and search results on your screen, flow from right to left. It allows you to enjoy your timeline in real time while doing other things, such as live commenting on a TV shows. Features Reply, Retweet and Fav any tweets Customize color and style of tweets Hide URLs in tweets Hide tweets around your cursor so it doesn't block your click
You may want to check out more Mac applications, such as PhoneAmego, iChatOnLogin or MySpaceIM, which might be similar to TweetRain.