What do you mean, mining code of the pool?
Each individual miner has his own code, and they submit shares to the pool - or am I mistaken?
in a pool the individual miners do not form the block.
the pool accepts or rejects transactions. and forms the cod that needs to be cracked, the miners just crack the code. send their solution to the pool. and if correct the pool gets the reward and publishes the finished block to all the miners. and the miners relay the solved block out to general public.
the pool then splits up the reward..
individual solo miners code is totally different then mining pools. for instance eligius has cod at the pool side to ignore a majority of zero fe transactions. and to give priority to large fee tx's. where as other pools do not have such rules.
yet the individual miners do not make this choice or need to download special code dependent on whichever pool you are on. its the pool owner that does all the protocol rule changes.