Well, that is some really nice Yew! Tight growth rings and looks prety clear from the pictures.
Now I would never buy kiln dried Yew but I have some good supliers of other hardwoods here in the Northwest that supply boat builders and they only take there wood down to arround 9 - 10% moisture content. It only causes problems when most woods are lower than 7%. I've made some great bows from kiln dried wood and never had any problems.