'Pure servers' will require that any clients will have to have exactly the same PAK files as the server they are logging into. So, if a server is running a default unmodified PAK set, everything should be AOK.
Never give in--never, never, never, never, in nothing great or small, large or petty, never give in except to convictions of honour and good sense. Never yield to force; never yield to the apparently overwhelming might of the enemy.
Winston Churchill, 1941.