BIOS files are owned by Nintendo. Because they are proprietary code, it is generally considered illegal to download them from the internet.
: Handles the ARM7 processor tasks, including sound, Wi-Fi, and touch screen input. Nintendo Ds Bios Image Files
: Dumping typically requires a Nintendo DS with a flashcart (like an R4) and a specialized homebrew tool like DSBFump or GodMode9i . Using BIOS Files in Emulators BIOS files are owned by Nintendo
: Certain games require the original BIOS to boot or function correctly. Nintendo Ds Bios Image Files
: The legal way to obtain these files is to "dump" them from your own physical Nintendo DS or DS Lite console.
: It enables the use of the actual system menu to change language settings or user profiles. Legal and Ethical Considerations