“Emulator” is a term of art in this area which refers to emulation of a hardware (and usually machine instruction) environment. Ironically, “translation” (as in instruction translation), as proposed by a sibling comment, is an even more connoted-with-hardware-emulation term.

WINE is … well, most directly it’s just an implementation of an API (the Windows APIs). In webdev parlance it might be called a “polyfill”. Perhaps a “compatibility shim”?