All wood furniture is made from "dead trees" :-)

Yes, you will need to dry it. The typical rule of thumb is 1 year per inch of thickness. To do otherwise is to risk warping and splitting as it dries. Store in a covered area with good ventilation. If you are going to cut it to width and thickness, now is the time. Wood "in the round" will almost almost always split because of differential shrinkage rates. If you are stacking the boards, separate them by "stickers" -- strips of wood going crosswise to the length. Keep the pile even and level.

But (seriously) dead wood can sometimes have rot, stains, spalting, or insect damage. Whether or not this is desirable depends a lot of your design and style. May or may not work for your application.

But for now, you have little to loose but time and effort.

yes, its just our time. :) we will cut it now, and store it to dry and then see what happens.
we have taken the bark off, and a top layer already. its pretty good with no bugs or damage. it was pretty dry.
thanks!
off to my workwork!!