Keeping the PSI low will help, but keeping it out of the refridgerator will not only limit and/or prevent it from carbonating, but it will also keep it at the proper serving temperature. The biggest hurdle though would be pouring it because I would assume that you are using a converted fridge and it wouldn't be in your best interest to put the keg in the fridge as stated above. You also will probably stain the lines and need to replace them if you switched back to beer. Your best bet is getting a single tap tower, splicing off your air line, putting a secondary regualtor for lower PSI, and mouting the tower on your bar. That said, seems like a costly endevour.