90% of the time a sticking caliper is caused by a bad BRAKE HOSE, not a bad caliper. Brake hoses, like calipers, should be replaced in pairs, because if one is bad the other is soon to follow. What happens is that the hose gets old and sorta spongey, so when you step on the pedal it expands, lets fluid through, and then collapses, trapping fluid in the caliper and causing the pads to drag. Of course a bad caliper will do this too, but like I said 90% of the time it is the hose, not the caliper, that has gone south. You are really supposed to replace the hoses any time you replace the calipers so its not like you are wasting money if you end up needing calipers anyway. Inspect your calipers, and if they look good just replace the hoses.

If you are leaking fluid from between the master cylinder and the brake booster your master cylinder is blown and needs to be replaced. The seals inside it have gone bad.