You need a copy of the game files (from your own old DVD or a trusted backup). The patch is free and legal because it modifies software you already physically own.
When the installer asks for a license key, cancel or skip if possible. If forced, you will need to find a community workaround (search for "Blur no-activation crack" – note that this is technically circumventing DRM, but for abandonware, it is widely tolerated). license key for blur pc game online