ExpressionsinBar 2.3 for Mac was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. ExpressionsinBar for Mac lies within Education Tools, more precisely Science. This software for Mac OS X is an intellectual property of Alelvisoftware.
From the developer:
ExpressionsinBar is a simple menubar application which provides powerful computer-aided algebra computations. A mathematical expression entered in the popup window is immediately computed and the result is displayed in an associated subview window. With the drag-and-drop feature, results are easily copied into text editors such as Pages or Microsoft Word, or presentation programs such as Keynote or Microsoft PowerPoint.
You may want to check out more software for Mac, such as LabAssistant, Calcline or Schematics Plus, which might be similar to ExpressionsinBar.