@AppStore 1.0 for Mac was available as a free download on our software library. The actual developer of this free software for Mac is Onemac.net.
From the developer:
Now you can follow the official Mac App Store tweet right from your Mac OS X Dashboard. Get hot app news, brand new releases, top featured apps, exclusive offers, updates, upgrades and much much more.
You may want to check out more Mac applications, such as TwitPic Uploader, Daylight or List My Apps, which might be related to @AppStore.