I promise I searched the comments some before asking this - is 4-palyer co-op possible online on the Steam version? I was impressed with the graphics and music. For what is probably (or looks to be) a simple game, this looks very well done.
You could use netplay using the ROM on your emulator of choice. My personal favorite is mednafen but it requires a bit of setup, Retroarch might be easier but I forget if it allows for 4 player.
