Buy Golden Gate at the Juiced.GS store
Golden Gate is a compatibility layer for ORCA (and GNO/ME) command line programs. Run text-based IIgs programs (including the ORCA/C, ORCA/M, ORCA/Pascal compilers) as if they were native.
Golden Gate is not an Apple IIgs emulator, per se. It's a 65816 emulator combined with a native implementation of the IIgs toolbox and GS/OS. There is no Mega II, no IWM, no video RAM, no keyboard strobes, no soft switches. But it turns out that most command-line utilities don't even care.