basically, PSARDumper allows you to "take apart" sony's Official Firmware Updates. This is useful when you need files for POPSLoader, a plugin for PSOne emulation, and also if you wish to run a game requiring a higher firmware than your CFW e.g. a game that requires 5.03 on 5.00m33-6. However for regular homebrew, you dont need this. If you plan on putting PSOne games on your PSP, then you may need to "dump" a few firmwares for use with POPSLoader, but otherwise you shouldnt need PSARDumper at all.