Download of DubStepPiano 1.0 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 lies within Audio & Video Tools, more precisely Music Production. According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software. The actual developer of this free Mac application is ButtonBass.
From the developer:
ButtonBass Dubstep Piano is a free application that allows you to play the Dubstep piano with your computer keyboard. This piano is loaded with dubstep loops for you to mix up to your hears content. You can switch the volume controls to stay visible by clicking the volume button on the right hand side of the piano.
You may want to check out more Mac applications, such as Mandala Virtual Brain, Bouncy or SmallScreen, which might be similar to DubStepPiano.