If they were stored properly they should be ok, although, i like to split all my logs soon after bringing them home to get them drying, keep them from deteriorating, and keep bugs from wanting them.
I generally just go at them with wedges a sledge and a hatchet to chop the stringers, but if the situation allows, I've been known to run a kerf down some straight-grained logs to better facilitate a predictable split.
4-6" logs aren't very big and you'll need accurate splits to make the most of the wood. Perhaps in this case, better options than outright splitting with sledge and wedges, assuming it's straight-grained, is to chalk a line and either kerf every split with a circular saw 1" deep, or just run it through a suitable sized bandsaw, cutting it into quarters.
Be VERY careful kerfing logs with a circular saw... hold on tight with both hands because it WILL kick back once in a while.