That looks like a pretty standard Sankey D coupler, I think. That's what you use to tap almost every domestic commercial keg.
Most people use Corny kegs with homebrew, so you'd need a ball or pin lock keg and the appropriate disconnects. You'll need to cut the lines and attach it to the disconnects.
I'm not sure why the gas line isn't hooked up to that coupler, but since that beer line looks pretty old anyway, I'd suggest that you replace all the lines. Get at least 10 feet of 3/16" ID beer line.
If you plan on running commercial kegs in addition to your homebrew, you can grab MFL fittings for that coupler and get some swivel nuts to put on your lines. Then (assuming you also get MFL disconnects for the Corny keg) you can quickly swap back and forth between the two.
