Download of FocusMask 1.1 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. This Mac app is a product of TenTrip LLC. The application lies within Theming Tools, more precisely Multiple Desktops. Please check the Mac app with an antivirus before launch as it is downloaded from the developer's website, and we cannot ensure that it is safe.
From the developer:
FocusMask is a simple concentration aid that allows you to hide clutter on your screen (without affecting the hidden windows). It lets you to put distractions out of sight and out of mind. Simply point your cursor at a window on your desktop, press a keyboard shortcut, and all the other objects competing for your attention will fade away into the background.
You may want to check out more Mac applications, such as NoMenuBar, Clocky or GreenOrbmax, which might be related to FocusMask.