It will help you overcome the limitations the newest PS3 firmware update sets to make it impossible for you to downgrade the firmware and then jailbreak it. PS3DJB utilizes the PSFreedom and PSDAndroid apps.
Oh by the way, the one who create the app is XDA-Developers forum member, named HackMimic. The guy just released the app to dismiss all the troubling process. You can simply download and install the app to your machine and if you are interested to downgrade and jailbreak your PS3 on HD2 using PS3DJB, then visit the instructions page from the following link below: