i'll bet that it is the slave cylinder that is frozen, i've seen that more than a rusted together clutch.
check this by pushing the rod in to the slave.
but if it is the clutch you can sometimes free them.
put a jumper wire in the connector for the clutch safety switch.
put the car in 2nd gear.
apply pressure to the clutch pedal and keep holding it, not too much cause you can bend the pedal.
turn the key and let the starter "walk" the car forward for 5 seconds.