BIOS files are owned by Nintendo. Because they are proprietary code, it is generally considered illegal to download them from the internet.
: Contains the system settings, user interface (the DS "menu"), and user-specific data like birthday and nickname. Why Are They Needed? Nintendo Ds Bios Image Files
Understanding Nintendo DS BIOS Image Files The consists of essential system files—specifically bios7.bin , bios9.bin , and firmware.bin —that serve as the "brain" of the original handheld hardware. These files are required by many emulators to accurately replicate the console's behavior, boot sequence, and system functions. What are Nintendo DS BIOS Files? BIOS files are owned by Nintendo
: It enables the use of the actual system menu to change language settings or user profiles. Legal and Ethical Considerations user interface (the DS "menu")