With open diffs, weather it's on the front or the rear, in 2 wheel drive, it shouldn't matter. Up front, it'll just work. It'll probably throw off the steering a little though. Out back, it'll become the drive wheel. It has to spin slightly faster to keep up with the non spare tire. This can throw off the speedometer. Even in full time with a 242, short distances shouldn't matter. I can see long term effects like stretching the chain if you drive it like that for an extended period of time. You would want to keep the transfer case unlocked though. You could damage it in part time with a smaller wheel up front or out back.
97 ZJ - 5.2L, 242, 4" IRO lift w/short arms & adj. TBs, JKS Discos/BPEs, DT3000s, Aussie'd 44A, sliders, OEM skids/hooks/hitch, 31" Duratracs on 15x8s
14 JKU Sport S - Stock