Good point - I'd misread you there.
From a quick google all I can find is No$GBA running two emulators on the same PC, and still there you get connection errors if your PC isn't fast enough to emulate them both full speed. Again, that's GBA rather than GameBoy but it's an indication. Still, the only way to find out is to try it, if you can convince any of the emulator maintainers to have a go.