This is a copy of the original release published on Google Code back on June 3rd, 2012.
For reference, it is the same download from https://code.google.com/archive/p/umd-file-renamer/downloads and the same reviewed by https://mac.softpedia.com/get/Games/UMD-File-Renamer.shtml and http://games.softpedia.com/get/Tools/UMD-File-Renamer.shtml (this last one broken by now).
Unzip all the contents of this zip file and run UMD_FileRenamer-1.0.jar using Java by double clicking it, or running java -jar UMD_FileRenamer-1.0.jar on a terminal or command prompt.