Version 5.2 or later of Doubletake uses mini-filter drivers and so does not require a reboot when upgrading or uninstalling. In order to ensure that a reboot is not prompted during the upgrade or uninstall process, however, you must stop all Doubletake services and kill any Doubletake processes running under any user on the server.
If any consoles are open or if the Doubletake.exe process is still running, a reboot may be required or a false positive message stating a reboot is required may appear.
Once all Doubletake services and executables are stopped, there will be no reboot required for Doubletake.
Doubletake does require certain C++ components and .NET 3.5.1 components for version 5.2 and later. If these are not present then an upgrade my require them to be installed and those 3rd party installations may require a reboot outside the Doubletake upgrade process.
This is rare as all C++ and .NET 3.5.1 compoenents should already exist on the server already running version 5.2 or later of Doubletake.