The V-STUDIO 20's drivers are both Windows (ASIO) and Mac (Core Audio) compatible; this means that the V-STUDIO 20 hardware itself can be used with Windows or Mac audio software that is ASIO or Core Audio compliant--which is most audio recording software in the industry. However, the Cakewalk Guitar Tracks Pro software bundled with the V-STUDIO 20 is Windows only. If you are using a Mac, you may use the V-STUDIO 20 hardware with Core Audio compliant audio software such as GarageBand, Logic, Audacity, etc.
If you would like to use the VS-20 with GarageBand or Logic, you may download the VS-20 Control Surface plug-in:
VS-20 Control Surface Plug-in for GarageBand and Logic
(Note: Installation and setup instructions are included with the download)