I received an email saying I have been able to write the deferred exam however it says "subject to the compliance of" student dropping courses to maintain a 4 courseload maximum. Do I absolutely HAVE to drop to write?

Hey Ash; I would recommend emailing your faculty to clarify but chances are, if it's a conditional deferral, they expect you to meet those requirements for whatever reasons (they may simply want to ensure you do well on all the courses you take + deferral next year).

What?? I would contact them. should I dont see why you have totake 4 courses next semester just to write a def exam in feb

I think they usually require you to lower your course load when you have deferred more then one exam. If that's the case you can kinda see where they are coming from.
If it was just that one exam you had deferred though then it shouldn't really be a reason to drop a class so I would email your faculty head. You might have to plea your case in a meeting.