GSplus is an Apple IIgs emulator. It's an open-source project based on the KEGS and GSPort emulators. It supports fullscreen, joysticks and audio through the SDL2 library across platforms.
The goals of this project are to make an easier to install and easier to use emulator, and to modernize the overall codebase and emulation platform.
While much work has been done, adding new drivers and features over the past year, it is still in alpha phase. Feel free to download the package for your platform and play around, but beware there are many bugs still.