It’s made by the same developer(s). Unlike simple64 however, it’s not based entirely on Mupen64Plus. And it’s aiming for a more LowSpec hardware overhang.
It uses parallel-RDP in correlation with an original interpreter based on observing the better components from the mupen64plus and ares interpreters in order to come out with something that’s a bit more universally efficient, and better compatible with different hardware.
It also contains some features that aren’t found in mupen64plus or ares, for example, SummerCart64/SD card emulation, CPU overclocking, Japanese VRU support, etc.
With the latest release of version 1.1.6 that adds save states and improved net-play support, I figured this one could be considered for candidacy in the Libretro department.
But I don’t know how it works behind the scenes. It’s entirely up to the people who run it. I’m just shooting suggestions in the dark.