uDock communicates with other programs and applications on your Mac. Eg. double clicking on an file in sends the "open" message to the file. Clicking on a process in the Process list sends the "activate" message to the Finder which brings the process to the front.
uDock needs Accessibility permissions to display icon badges and a list of other apps' windows (the website version). To grant the Accessibility permissions, open System Preferences, click Security & Privacy icon, select Privacy tab and select "Accessibility" from the list on the left:
Then click the lock icon at the bottom to make changes. On the list select uDock checkbox:
If uDock is not on the list, click "plus" button to add it: