Blur is currently in a state of limbo. Because Activision lost the car licenses (Ford, BMW, etc.), they cannot legally sell the game anymore. This makes it "Abandonware."
Stay safe, keep your firmware updated, and always dump your own UMDs whenever possible.
: Because there is no official ISO, many sites claiming to offer a "Blur PSP Download" are often hosting fake files, malware, or incorrect ROMs. How to Play Blur Today
If you want, I can:
You download the file, transfer it to your PSP’s ISO folder, and boot it up. Instead of Blur , you are greeted by: