A: The Melonds emulator itself is legal open-source software. However, the Nandbin and BIOS files are copyrighted by Nintendo. You are legally required to dump these files from a Nintendo DSi that you personally own.
Implementing the Nandbin Melonds concept requires a multi-faceted approach: nandbin melonds
To understand Nandbin MelonDS, one must first understand the state of Nintendo DS emulation in the late 2010s. For years, was the only viable option—stable but notoriously single-threaded, slow on ARM-based devices (like early Raspberry Pis and smartphones), and lacking certain hardware-accurate features. Then came MelonDS (by StapleButter), a ground-up emulator focused on accuracy over speed. MelonDS brought near-perfect Wi-Fi emulation, JIT recompilers, and excellent game compatibility. A: The Melonds emulator itself is legal open-source software