This version of Active Trader Pro for the Mac does not require a Windows operating system. This solution leverages CrossOver, a compatibility layer software, which allows applications designed for Windows to run on other operating systems.
If you are currently using Parallels to run multiple Windows applications, including Active Trader Pro, you can continue to do so.
If you are using Parallels solely to run Active Trader Pro, you can take advantage of this version; it doesn't require a Windows license (like Parallels does) and doesn't incur the performance penalties associated with running a Virtual Machine and the full Windows OS on the Virtual Machine.