Fretello 2.5.2 for Mac could be downloaded 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. The actual developer of this free software for Mac is Fretello GmbH. Fretello for Mac relates to Education Tools.
From the developer:
Fretello provides music lessons for beginners. The application includes step-by-step guitar lessons so you can master the chords, discover your sound, and learn playing songs. You simply download Fretello, grab your guitar, and start advancing. You will be able to play your first riff and improve your sound and technique.
You may want to check out more Mac applications, such as Planbook, ClaroRead or TimeFlyer, which might be related to Fretello.