RMG v0.1.8 is released. Rosalie's Mupen GUI is a free and open-source mupen64plus GUI written in C++. It offers a simple-to-use user interface.

RMG changelog:
Add transfer pak support to RMG-Input (93c75a5)
Add real-time controller pak switching to RMG-Input (994e358)
Account for input device in per game settings in RMG-Input (44f8f6b)
Fix keyboard configuration in RMG-Input (7da0033)

Download: RMG v0.1.8
Source:Here