The Demo version is free, but has a limited duration license. You will need to come back here every couple of months to download a new installer if you want to keep on using UVLayout.
Download the UVLayout DMG file, then open it up and follow the instructions in the Read-Me.txt file. Plus if you don’t already have XQuartz installed, download and install that as well. See Installation_Guide:_OS_X for full installation instructions.
After installation, you can run UVLayout by drag’n’dropping OBJ files onto the “UVLayout Demo” application icon.