Download of DejaDesktop 1.2.1 for Mac was available 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. DejaDesktop for Mac is included in Theming Tools. The actual developer of this free Mac application is CompanionLink Software, Inc.
From the developer:
DejaDesktop lets you add a free monthly Calendar to your macOS wallpaper. The application is ideal for anyone who schedules things in advance. The data feed allows you to add a day view and to show all appointments scheduled for the day. In addition, it offers quick lists of Tasks, Contacts, and Notes.
You may want to check out more software for Mac, such as DejaDesktop Calendar Wallpaper, which might be similar to DejaDesktop.