Brother does not publicly host this file for consumers. Downloads found on file-sharing threads or tech forums like the Spiceworks Community are highly prone to carrying malware.
The tool may run in the background to monitor for firmware updates or status reporting. Brother Printer Driver Utility Brmainte.exe
If the file seems to be missing, it might have been accidentally deleted or not properly installed. Reinstall the printer drivers. Brother does not publicly host this file for consumers