Solution: The file needs to be unstuffed. Most Macintosh computers with Stuff-it or similar data compression software installed correctly will automatically unstuff a binhex file when it is clicked on.

Open your data compression software, such as Stuff-it. From the file menu select expand and choose the LexiverbTDMQD3Dinstaller.bin. The file will expand into the executable Lexiverb demo installer.